Regional Climate Models (RCMs) have become fundamental tools to study climate processes and
climate change projections at the regional to local scale, and the COordinated Regional Downscaling EXperiment (CORDEX) has become a central program within the RCM modeling community. This session accepts papers on a wide range of topics pertaining the field regional climate modeling and applications, including: recent developments in RCM science; added value of RCMs; applications of RCMs to regional climate change projection; development and application of coupled regional Earth System Models (including interactive atmosphere, ocean, chemistry/aerosol, biosphere and cryosphere components); development and application of convection-permitting RCMs; completion and/or analysis of CORDEX experiments, both single model simulations and multi-model ensembles; completion and/or analysis of experiments within the CORDEX-CORE and CORDEX Flagship Pilot Studies programs; application of RCM output to vulnerability, impacts and adaptation studies; application of RCMs to climate service activities.
vPICO presentations: Mon, 26 Apr
Compared to standard regional climate models (RCMs), convection-permitting models (CPMs) provide an improved representation of sub-daily precipitation statistics and extremes thanks mainly to the possibility to switch off the deep convection parameterisation, a known source of model error and uncertainties. The more realistic representation of local processes in CPMs leads to a greater confidence in their projections of future changes in short-duration precipitation extremes. Recent literature on CPMs seems to agree on a future increase of extreme precipitation, above Clausius‐Clapeyron scaling in some cases, which is likely to have severe socio-economic impacts.
The quantification of uncertainties on future changes at this resolution has been barely touched. Using the first‐ever ensemble of CPMs run within the UK Climate Projections project, Fosser et al. (2020) found that the climate change signal for extreme summer precipitation may converge in CPMs in contrast to RCMs, thanks to a more realistic representation of the local storm dynamics.
Here we use the first multi-model CPMs ensemble over the greater Alpine region, run under the auspices of the World Climate Research Programme’s (WCRP) Coordinated Regional Downscaling Experiment Flagship Pilot Study on Convective phenomena at high resolution over Europe and the Mediterranean (Coppola et al. 2020). In our analysis we compared the uncertainties in the CPMs ensemble to the driving models following a similar method to Fosser et al. (2020). In this presentation we will show if multi-model CPMs can really provide more certain extreme rainfall projections then their parent coarser resolution models.
Fosser G, Kendon EJ, Stephenson D, Tucker S (2020) Convection‐Permitting Models Offer Promise of More Certain Extreme Rainfall Projections. Geophys Res Lett 47:0–2. doi: 10.1029/2020GL088151
Coppola, E., Sobolowski, S., Pichelli, E. et al. A first-of-its-kind multi-model convection permitting ensemble for investigating convective phenomena over Europe and the Mediterranean. Clim Dyn 55, 3–34 (2020). https://doi.org/10.1007/s00382-018-4521-8
How to cite: Fosser, G., Adinolfi, M., Ban, N., Belusic, D., Berthou, S., Caillaud, C., Cardoso, R. M., Coppola, E., De Vries, H., Dobler, A., Feldmann, H., Goergen, K., Kendon, E. J., Lenderink, G., Panitz, H.-J., Pichelli, E., Soares, P. M. M., Somot, S., Tölle, M. H., and Vergara-Temprado, J.: Can Convection‐Permitting Models really Offer Promise of More Certain Extreme Rainfall Projections ?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11001, https://doi.org/10.5194/egusphere-egu21-11001, 2021.
The World Climate Research Programme (WCRP) has an international initiative called the COordinated Regional climate Downscaling EXperiment (CORDEX). The goal of the initiative is to provide regionally downscaled climate projections for most land regions of the globe, as a compliment to the global climate model projections performed within the Coupled Model Intercomparison Projects (CMIP). CORDEX includes data from both dynamical and statistical downscaling. It is anticipated that the CORDEX dataset will provide a link to the impacts and adaptation community through its better resolution and regional focus. Participation in CORDEX is open and any researchers performing climate downscaling are encourage to engage with the initiative. Here I present the current status, evaluation and future projections for the CORDEX-AustralAsia ensemble.
The CORDEX-Australasia ensemble is the largest regional climate projection ensemble ever created for the region. It is a 20-member ensemble made by 6 regional climate models downscaling 11 global climate models. Overall the ensemble produces a good representation of recent climate. Consistent biases within the ensemble include an underestimation of the diurnal temperature range and an underestimation of precipitation across much of southern Australia. Under a high emissions scenario projected temperature changes by the end of the twenty-first century reach ~ 5 K in the interior of Australia with smaller increases found toward the coast. Projected precipitation changes are towards drying, particularly in the most populated areas of the southwest and southeast of the continent. The projected precipitation change is very seasonal with summer projected to see little change leaning toward an increase. These results provide a foundation enabling future studies of regional climate changes, climate change impacts, and adaptation options for Australia.
How to cite: Evans, J., Di Virgilio, G., Hirsch, A., Hoffmann, P., Reca Remedio, A., Ji, F., Rockel, B., and Coppola, E.: The CORDEX‐Australasia ensemble: evaluation and future projections, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-81, https://doi.org/10.5194/egusphere-egu21-81, 2020.
The answers to the following questions ‘What are the consequences of climate change (warming)…?’ and ‘By when do we have to be prepared for that level of climate change (warming)?’ must be given only with caution. On the one hand, regional or local changes can be inconsistent with global changes, as local processes might not accurately interpreted by global climate models (GCMs) due to their relative coarse resolution. On the other hand, climate model simulations’ outputs are prone to biases compared to observations; furthermore, climate projections can be very different in modelling future temperature characteristics. In this context, while the magnitude of expected change described by a climate model may seem to be reasonable, but the projected temperature is not necessarily realistic (considering the model’s relative bias compared to observations). More specifically, the standard procedure of assessing climate change can be illustrated by taking the mean for a future period (e.g. 2070–2099) and compute the change relative to a reference period (e.g. 1976−2005). Keeping in mind the expected changes based on those projections might come with high degree of uncertainty as simulations might show different mean temperature values for the same assessed periods with even a range of few degrees of °C. When regional climate change is assessed based on at a given regional warming level (WL, e.g. 1.5 °C) added to the observed mean, then the aforementioned uncertainty range is reduced as the models (GCM or regional climate models) are assessed with respect to the same 30-year mean temperature value, but not for the same periods (noting that the WL is defined at regional and not at global scale). Thus the uncertainty of expected changes with regard to temperature can be significantly reduced. In this case an additional uncertainty factor might rise: time, as climate models can reach that WL at different times. Accordingly, we can give information on relative changes with a specific uncertainty as a metric based on the timing of reaching the assessed WL. Aim of the present work is to illustrate the feasibility of this concept for the region of the Carpathian Basin based on high-resolution EURO- and Med-CORDEX simulations.
How to cite: Torma, C. Z.: Investigation of future climate characteristics over the Carpathian Region by “tuning” CORDEX temperature time series – a new perspective, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-570, https://doi.org/10.5194/egusphere-egu21-570, 2021.
Many observation-based and modelling studies have identified the Eastern Mediterranean and Middle East (EMME) region as a prominent climate change hot-spot. During the last half century, the region has warmed faster than the global mean, while at the same time changes in the hydrological cycle have been observed. Several studies suggest that these trends are projected to continue and intensify throughout the 21st century, depending on greenhouse gas emission scenarios. To assess climate change impacts on a regional and local level, future climate information of high quality and spatial resolution is required. To provide such information is the objective of CORDEX. The latest advancement of this World Climate Research Programme (WCRP) initiative includes the CORDEX-CORE set of regional experiments that aims at global coverage and was designed to provide regional-level information to the upcoming Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). This state-of-the-art dataset is available at a spatial resolution of 0.22° (about 25 km). We have complemented this ensemble model data with those from two experiments of the MENA-CORDEX initiative that are available at the same resolution. Here, we have analyzed monthly data from 1971 to the end of the current century. We have adopted a multi-domain and multi-model ensemble approach that is found to add value by addressing shortcomings and reducing uncertainties. Our results corroborate and update existing estimations on the transition to drier and hotter conditions in the EMME region. Under a business-as-usual pathway (RCP8.5), the region-average warming at the end of the current century is expected to exceed 5 °C (with respect to the 1986-2005 reference temperature). On the contrary, under a strong mitigation pathway (RCP2.6) this warming can be limited to less than 1.5 °C. Summer warming is projected to exceed these values by 2-3 °C, favoring the conditions for unprecedented heatwaves. On average, precipitation changes are less robust and significant and range between 0 to -15% of the reference values, while locally stronger drying can occur, particularly under RCP8.5.
How to cite: Zittis, G., Hadjinicolaou, P., and Lelieveld, J.: Climate change projections for the eastern Mediterranean and the Middle East based on CORDEX-CORE simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1175, https://doi.org/10.5194/egusphere-egu21-1175, 2021.
The Euro-Mediterranean region is subject to numerous and various aerosol loads, which interact with radiation, clouds and atmospheric dynamics, with ensuing impact on regional climate. However up to now, aerosol variations are hardly taken into account in most regional climate simulations, although anthropogenic emissions have been dramatically reduced in Europe since the 1980s. Moreover, inconsistencies between regional climate models (RCMs) and their driving global model (GCM) have recently been identified in terms of future radiation and temperature evolution, which could be related to the differences in aerosol forcing.
The present study aims at assessing the role of aerosols in the future evolution of the Euro-Mediterranean climate, using a specific multi-model protocol carried out in the Flagship Pilot Study "Aerosol" of the CORDEX program. This protocol relies on three simulations for each RCM: a historical run (1971-2000) and two future RCP8.5 simulations (2021-2050), a first one with evolving aerosols, and a second one with the same aerosols as in the historical period. Six modeling groups have taken part in this protocol, providing nine triplets of simulations. The analysis of these simulations will be presented here. First results show that the future evolution of aerosols has a significant impact on the evolution of surface radiation and surface temperature. In addition RCM runs taking into account the evolution of aerosols are simulating climate change signal closer to the one of their driving GCM than those with constant aerosols.
How to cite: Nabat, P., Somot, S., Corre, L., Katragkou, E., Li, S., Mallet, M., van Meijgaard, E., Pavlidis, V., Pietikäinen, J.-P., Soerland, S., and Solmon, F.: Impact of aerosols on the future Euro-Mediterranean climate: results from the CORDEX FPS-Aerosol, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2211, https://doi.org/10.5194/egusphere-egu21-2211, 2021.
Medicanes are tropical-like cyclones that form in the Mediterranean Sea. Due to their harmful potential, the characterization of medicanes has become an increasingly-studied topic within the scientific community. In the current context of climate change, their future characterization from a climatological perspective can only be attained using high resolution climate model output. The thermal structure of medicanes is generally examined with the Cyclone Phase Space (CPS) described in Hart (2003). This necessitates geopotential data from 300 hPa to 900 hPa every 50 hPa. Notwithstanding, in long, high-resolution climate simulations, model output requires very high storage space and only data from a few geopotential levels are typically saved. To overcome the lack of geopotential data at some levels, available model data are vertically interpolated in order to obtain data for the 13 levels required. In this work, we use high horizontal resolution data from the ERA-5 reanalysis (1979 - 2018) to analyze the climatology of medicanes simulated using the 13 vertical levels required based on Hart (2003), as well as different combinations of geopotential data from a few selected levels. Our results allow us to propose, for the first time, a limited set of recommended geopotential levels needed to adequately detect medicanes in long, high resolution climate change simulations, taking into account the associated limitations of output data storage.
How to cite: de la Vara, A., Gutiérrez-Fernández, J., González-Alemán, J. J., and Gaertner, M. Á.: A proposal for medicane detection in long high-resolution climate model simulations with a minimal amount of data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2948, https://doi.org/10.5194/egusphere-egu21-2948, 2021.
This study evaluates the possible impacts of climate change on Surface Solar Radiation (SSR), as a renewable energy resource, in Southern Africa (SA). Performance of climate models in reproducing the mean states and long-term trend of SSR are assessed by validating five Regional Climate Models (RCM) that participated in the Coordinated Regional Downscaling Experiment program over Africa (CORDEX-Africa) along with their ten driving General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) over SA. Then the possible impacts of climate change on SSR are evaluated. The uncertainties in the GCM-RCM model chains have also been quantitatively estimated.
Results show that in the past (1) GCMs overestimate SSR over SA in terms of their multi-model mean by about 1 W/m2 (compensation of opposite biases over sub-regions) and 7.5 W/m2 in austral summer and winter respectively compared to SARAH-2 (Surface Solar Radiation Data Set—Heliosat Edition 2); However, RCMs underestimate SSR in both seasons with Mean Bias Errors of about −30 W/m2in austral summer and about −14 W/m2 in winter. And the discrepancies in the simulated SSR are larger in the RCMs than in the GCMs. (2) In terms of trend during the “brightening” period 1990–2005, both GCMs and RCMs (driven by ERA-Interim and GCMs) simulate an SSR trend of less than 1 W/m2 per decade. However, variations of SSR trend exist among different references data. (3) For individual RCM models, their SSR bias fields seem rather insensitive with respect to the different lateral forcings provided by ERA-INTERIM and various GCMs, in line with previous findings over Europe.
In future, (1) multi-model mean projections of SSR trends are consistent between the GCMs and their nested RCMs. Two areas with statistically significant SSR changes are found: over the center of SA, GCMs and RCMs project a statistically significant increase in SSR by 2099 of about +1.5 W/m2 per decade in RCP8.5 during the DJF season. Over Eastern Equatorial Africa a statistically significant decrease in SSR of about −2 W/m2 per decade in RCP8.5 is found in the ensemble means in DJF. (3) SSR projections are fairly similar between RCP8.5 and RCP4.5 before 2050 and then the differences between those two scenarios increase up to about 1 W/m2 per decade with larger changes in RCP8.5 than in RCP4.5 scenario. (4) These SSR evolutions are generally consistent with projected changes in Cloud Cover Fraction over SA and may also related to the changes in atmosphere water vapor content. (5) SSR change signals emerge earlier out of internal variability estimated from ERA-Interim in DJF in RCMs than in GCMs, which suggests a higher sensitivity of RCMs to the forcing RCP scenarios than their driving GCMs in simulating SSR changes. (6) The uncertainty in SSR change projections is likely dominated by the internal climate variability before 2050, and after that model and scenario uncertainties become as important as internal variability until the end of the 21st century.
How to cite: Tang, C., Morel, B., Wild, M., Pohl, B., Abiodun, B., Lennard, C., and Bessafi, M.: numerical simulations of Surface Solar Radiation over southern Africa for the past and future, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3811, https://doi.org/10.5194/egusphere-egu21-3811, 2021.
Coarse resolution global climate models (GCM) cannot resolve fine-scale drivers of regional climate, which is the scale where climate adaptation decisions are made. Regional climate models (RCMs) generate high-resolution projections by dynamically downscaling GCM outputs. However, evidence of where and when downscaling provides new information about both the current climate (added value, AV) and projected climate change signals, relative to driving data, is lacking. Seasons and locations where CORDEX-Australasia ERA-Interim and GCM-driven RCMs show AV for mean and extreme precipitation and temperature are identified. A new concept is introduced, ‘realised added value’, that identifies where and when RCMs simultaneously add value in the present climate and project a different climate change signal, thus suggesting plausible improvements in future climate projections by RCMs. ERA-Interim-driven RCMs add value to the simulation of summer-time mean precipitation, especially over northern and eastern Australia. GCM-driven RCMs show AV for precipitation over complex orography in south-eastern Australia during winter and widespread AV for mean and extreme minimum temperature during both seasons, especially over coastal and high-altitude areas. RCM projections of decreased winter rainfall over the Australian Alps and decreased summer rainfall over northern Australia are collocated with notable realised added value. Realised added value averaged across models, variables, seasons and statistics is evident across the majority of Australia and shows where plausible improvements in future climate projections are conferred by RCMs. This assessment of varying RCM capabilities to provide realised added value to GCM projections can be applied globally to inform climate adaptation and model development.
How to cite: Di Virgilio, G., Evans, J. P., Di Luca, A., Grose, M. R., Round, V., and Thatcher, M.: Realised added value in dynamical downscaling of Australian climate change, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3855, https://doi.org/10.5194/egusphere-egu21-3855, 2021.
Climate models play an important role in global and regional climate change research, improving our understanding and predictability of climate behaviour. The CORDEX (Coordinated Regional Downscaling Experiment) program was established to provide a framework for the assessment of Regional Climate Models (RCMs) and to contribute to climate change impact assessment and adaptation processes. The climate simulations are based on multiple dynamical and empirical-statistical downscaling models forced by multiple global climate models (GCMs). The motivation behind the use of multiple models in climate change research is to cover different sources of uncertainties, that is why it is recommended to use all available simulations in climate change studies. However, many climate change impact studies face difficulties (e.g., limited computing resources or free access to climate data) using all the available simulations, and therefore it is quite often the case that only subsets of simulations are used. Another problem is that the ensembles of GCM-RCM simulations are too big to be handled by many impact modellers. The selection of model simulations is subjective in most cases, and it is often reduced by hand-picking climate simulations depending on the partners involved in the project. An objective method can be based on cluster analysis, which is a flexible and unsupervised numerical technique that involves the sorting of data into statistically similar groups. These groups can be either (i) determined entirely by the properties of the data themselves or (ii) guided by user constraints. In the present study, we focus on Central-Eastern Europe, because the model simulations are particularly uncertain in the precipitation and temperature distribution over this region. The aim of the study is to develop a method based on the precipitation and temperature values of 55 EURO-CORDEX simulations for a near-present historical period (1995–2014), which could help to select suitable subsets of ensembles of climate simulations tailored to the needs within climate change impact studies.
Acknowledgement: This study is supported by the ÚNKP-20-3 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research, Development and Innovation Fund.
How to cite: Kalmár, T., Pongrácz, R., and Pieczka, I.: Cluster analysis of the ensembles of EURO-CORDEX simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4738, https://doi.org/10.5194/egusphere-egu21-4738, 2021.
Extreme precipitation events with return periods above 100-years (Most Extreme Precipitation Events; MEPE) are rare events by definition, as the observational record covers very few of such events. Therefore, our knowledge is insufficient to assess their potential intensities and physical processes on different scales. To fill this gap, large regional climate ensembles, like the one provided by the German Decadal Climate Predictions (MiKlip) project (> 10.000 years), are of great value as they provide a larger sample size of such rare events. The RCM ensemble samples present day climate conditions multiple times (Ehmele et al., 2020) with a resolution of 25 km, and thus it does not resolve the convection permitting scales (CPM).
In this study, we aim to combine the large RCM ensemble with episodic CPM-scale downscaling simulations to derive a better statistical and process related representation of MEPEs for Central Europe. As a first step, we evaluate two re-analysis driven long-term simulations with COSMO-CLM (CCLM) from MiKlip and CORDEX-FPS Convection with respect to their scale-dependent representation.
The simulations span the period 1971 to 2016 with the 25 km simulation and are forced by ERA40 until 1979 and by ERA-interim afterwards. The CPM simulation (~3 km) is forced by ERA-40 between 1971 and 1999 and by ERA-interim between 2000 and 2016. We validate the simulations against E-OBS (25 km) and the unique HYdrologische RASterdatensätze (HYRAS) precipitation data set (5 km). The investigation area is the greater Alpine area. We employ a Precipitation Severity Index (PSI) adapted from extreme wind detection (Leckebusch et al., 2008; Pinto et al., 2012) for extreme precipitation cases. The advantage of the PSI is its ability to account for extreme grid point precipitation as well as spatial coverage and event duration. The events are categorized objectively into composite Weather Types (WT) to enable further generalization of the findings.
The results show a clear overestimation of precipitation for the analysed period and area by the RCMs at both resolutions. However, large differences exist the representation of extreme precipitation. Compared to observations, the 3 km (25km) resolution overestimates (underestimates) precipitation intensity for extreme cases. This agrees with previous literature. Five different WTs are identified for the analysed period, with Autumn-Winter WT being the most common, followed by convective summer WT. The Autumn-Winter WT is characterized by deep, cold, low-pressure areas located over Northern Europe. Summer WT cases are characterized by stable high-pressure situations affected by incurring small low-pressure systems on its western flank (convective-prone situations). Regarding the scale dependency of precipitation processes, the coarse resolution tends to overestimate surface moisture in situations of heavy precipitation, leading to larger latent instability (CAPE) in the 25 km resolution than in its 3 km counterpart. Furthermore, a large-scale dependency is found in summer extreme precipitation cases for two stability-related variables, Equivalent Potential Temperature (θe850) at 850 hPa and moisture flux at the Lower Free Troposphere (LFT-moisture). In these cases, the overestimation (underestimation) of and LFT-moisture by either resolution is in line with their precipitation overestimation (underestimation).
How to cite: Caldas-Alvarez, A., Feldmann, H., and Pinto, J. G.: Scale-dependent representation of extreme precipitation processes in regional and CPM scale simulations for the greater Alpine region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4852, https://doi.org/10.5194/egusphere-egu21-4852, 2021.
Compound events of weather extremes considerably affect various sectors of human society and natural environment and therefore it is essential to understand projected changes of their characteristics in the future climate. We focus on the combination of low temperature and high wind velocity, because their compound effect strongly influences human thermal comfort in cold weather, as characterized by the wind chill factor. In our study, we analyse frequency of this extreme events and projected changes of their characteristics in simulations of RCMs from the EURO-CORDEX project. We investigate a set of 9 simulations of 3 different RCMs driven by 3 different global climate models which allow us to analyse the influence of driving data on the RCM’s outputs. We focus on the Central European domain defined between 48–52°N and 10–19°E. The frequency of the compound events from historical simulations over 1970-2100 are compared to the projected frequencies under the RCP4.5 and RCP8.5 emission scenarios for the end of the 21st century (2070-2100). Since local climate is relatively tightly linked to a large-scale atmospheric circulation over Europe in winter, we also evaluate links of the compound events to the atmospheric circulation.
How to cite: Plavcová, E., Lhotka, O., and Stryhal, J.: Projected changes in frequency of compound events of strong wind and low temperature in EURO-CORDEX climate models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4994, https://doi.org/10.5194/egusphere-egu21-4994, 2021.
Downscaling has been widely used in studies of regional and/or local climate as it yields greater spatial resolution than general circulation models (GCM) can provide. It can approached in two distinct ways: 1) Statistical and 2) Dynamical. Statistical downscaling utilizes mathematical relationships between large-scale and regional/local climate to transform GCM or reanalysis data to a higher spatial resolution. Dynamical downscaling comprises forcing the lateral boundaries of a regional climate model with reanalysis or GCM data. However, there is no set technique to select said GCM(s).
A comprehensive yet easily applicable selection procedure was created to address this. Using reanalysis data and/or observational data, the space-time climatic anomalies and the mean state of the climate are evaluated for the region of interest. East Africa was utilized as a case study and GISS-E2-H r6i1p3 was found to perform the strongest. This procedure cannot, however, tell whether the models can reproduce the key processes of the region. To examine this, the ability of the models to simulate the Indian Ocean Dipole were evaluated. It was found that higher ranked models were better able to capture it than lower ranked ones. Furthermore, to ensure that a higher ranked model yielded a better downscaling simulation, three 10-year regional climate model simulations over East Africa were undertaken, where they were respectively forced by the highest ranked GCM (GISS-E2-H r6i1p3), the lowest ranked GCM (IPSL-CM5A-LR r4i1p1) and the MERRA-2 reanalysis product. The simulated surface temperature and precipitation for Equatorial East Africa were compared with a gridded observational dataset (CRU TS 4.04). Results showed that the higher ranked GCM produced a better downscaled simulation than the lower ranked one, a result that was more evident for surface temperature than precipitation.
How to cite: Pickler, C. and Mölg, T.: GCM Model Selection Procedure for Downscaling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5153, https://doi.org/10.5194/egusphere-egu21-5153, 2021.
Changes in global fire activity are influenced by a multitude of factors including land-cover change, policies, and climatic conditions. In this study we focus our attention on climate, investigating how relative humidity, wind, temperature and precipitation changes can act together in fire danger. Within the CORDEX-CORE initiative, two regional climate models (RCM) have been used at 0.22° resolution and to downscale 3 global climate models (GCMs) from the CMIP5 project. The analysis is carried out over 9 CORDEX domains for two climate scenarios namely the RCP2.6 and the RCP8.5. The high resolution regional climate simulations have been used to evaluate changes in the fire danger by means of the Fire Weather Index (FWI). The attention is focused on the Mediterranean Basin and in South America, as well as in Australia and in the North America domains. Both climate scenarios show similar projections for the near future time slice (2031-2050) with an increase of the index in those areas that are already affected by seasonal fires such as Spain and Southern Italy for the Mediterranean Basin and the central band of Brazil. For the future time slice (2081-2100) the signal increases, and it is stronger for the RCP8.5 scenario in all regions as expected.
How to cite: Raffaele, F. and Nogherotto, R.: Projections of the Fire Weather Index (FWI) using CORDEX-CORE simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5389, https://doi.org/10.5194/egusphere-egu21-5389, 2021.
Subtropical cyclones (SCs) climatology is evaluated in three simulations of Regional Climate Modeling version 4 (RegCM4) and in its global climate models (GCMs) drivers (HadGEM2-ES, MPI-ESM-MR and GFDL-ESM2M) over the South America domain. Three algorithms are applied to identify the SCs: the first tracks all cyclones, the second computes the thermal structure of the cyclones based on the Cyclone Phase Space (CPS) methodology, and the third automatically selects only the cyclones with subtropical features. After that, two ensembles were performed (RegCM4 and GCMs) and their climatologies are validated through comparisons with ERA-Interim reanalysis for the period 1979-2005. Over the southwestern South Atlantic Ocean, the annual average and standard deviation of SCs are 8.0± 2.5, 7.6± 2.3 and 7.2± 3.0, respectively, in ERA-Interim, RegCM4 and GCMs. Although both ensembles have a good performance in simulating the climatology of SCs, RegCM4 over perform the GCMs showing a better skill in representing both the annual mean and the interannual variability measured by the standard deviation. Moreover, RegCM4 simulates the spatial pattern of the cyclogenesis density closer to ERA-Interim than GCMs, which is another added value of the regional downscaling. SCs represent a small fraction of all cyclones over the region, which is 4.1% in ERA-Interim and GCMs and 3.5% in RegCM4. The relative importance of SCs to the total of cyclones increased to ~40% in the region near the southeast coast of Brazil. In terms of seasonal mean, simulations are able to capture the observed pattern that has the austral summer as the most cyclogenetic season.
How to cite: da Rocha, R., de Jesus, E., Reboita, M., Crespo, N., and Gozzo, L.: Performance of RegCM4 in Simulating Subtropical Cyclones over the Southwestern South Atlantic Ocean , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5900, https://doi.org/10.5194/egusphere-egu21-5900, 2021.
Dangerous weather related to severe thunderstorms including tornadoes, high-winds, and hail cause significant damage globally to life and property every year. Yet the impact on these storms from a warming climate remains a difficult task due to their small scale and transient nature. Here, we present a study in which the changes to the large-scale environments in which severe thunderstorms form were investigated during 21st century warming (RCP2.6 and RCP8.5) in a group of RegCM CORDEX-CORE simulations. Severe potential is measured in terms of CAPE (Convective Available Potential Energy) and shear during the severe seasons in three regions which are known to currently be prone to severe hazards: North America, the southeastern coast of South America east of the Andes, and eastern India and Bangladesh. In every region environments supportive for severe thunderstorms are projected to increase during the warm season months in both RCP2.6 and RCP8.5 during the 21st century. The number of days supportive for severe thunderstorms increases by several days per season over the vast majority of each region by the end of the century. In the case of RCP2.6, where greenhouse gas forcing is relatively weak compared to RCP8.5, there is still a consistent positive trend in the impact on severe days. The simulations using RCP8.5 forcing show large changes to the annual cycle of severe weather as well as the number of days supportive for severe weather per season. In some regions, like for example Northern Argentina along the Andes mountains, the number of days with severe conditions present increases by nearly 100% by the end of the century. Analyzing the CAPE and shear trends during the 21st century we find seasonal and regionally specific changes driving the increased severe potential. 21st century surface warming is clearly driving a robust increase in CAPE in all regions, however poleward displacement of vertical shear in the future leads to the movement of severe environments over North America and South America. We would also like to present a preliminary look at the next phase of this project which will apply similar methods to an ensemble of 11o Euro-CORDEX simulations to investigate severe conditions over the European region in the future.
How to cite: Glazer, R., Torres‑Alavez, J. A., Giorgi, F., Coppola, E., Das, S., Ashfaq, M., and Sines, T.: Projected changes to severe thunderstorm environments as a result of 21st century warming in CORDEX-CORE simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6282, https://doi.org/10.5194/egusphere-egu21-6282, 2021.
Interactions between land and atmosphere play an important role in the climate system on a wide range of spatial and time scales. Soil moisture is of particular importance as it constrains evapotranspiration, thereby affecting the surface energy and water balance. This influence then extends to extreme events such as droughts and heatwaves and even manifests as a local source of predictability.
Several studies suggest that high resolution model simulations which explicitly resolve convective processes can present substantially different soil moisture-precipitation feedback compared to simulations where convection is parameterized. In some instances, this feedback even changes sign between the two. The cause is from different soil moisture content (mostly in summer season) in parameterized vs. explicit simulations, which results in a different partitioning between heat fluxes, in turn modulating the amplitude and persistence of heatwave events.
The present study investigates modulation of heatwaves in km-scale convection permitting simulations during the 2000-2009 period. A second research topic is understanding whether km-scale modeling is beneficial for the representation of this phenomenon. Here, we consider a subset of five WRF RCM simulations within the CORDEX Convection Flagship Pilot Study. Further simulations from other modeling consortia are currently being analyzed for a truly multi-model perspective.
The analyses focus on the comparison of heatwaves simulated at convection resolving (~3km grid spacing) and non-convection resolving (~15km grid spacing) scales for each RCM. The five RCMs constitute a small multi-physics ensemble, where each member presents a different setup in terms of combinations of physical schemes. Analyses cover three different subdomains of the greater Alpine region: the Alps, Po valley, and Adriatic region.
Preliminary results show that, at very high resolutions with explicitly resolved convection, heatwave events exhibit lower soil moisture content than coarser resolution simulations. This feature affects the surface energy balance in terms of heat fluxes partition, with a subsequent impact on the maximum temperature, which is higher in the convection permitting simulations and generally in better agreement with observations. However, the heatwave maximum temperature modulation produced at the convection permitting scale, cannot be fully explained by differences in heat fluxes partition. This aspect suggests that also a different representation of small-scale circulation features is likely to play a role in determining the temperature modulation.
For areas with complex topography (e.g., Alps), results indicate a more consistent topography-driven soil moisture spatial patterns and related temporal evolution during heatwaves. At the same time, over different domains (e.g., Po valley) an excessive drying in the convection permitting RCMs is observed.
Finally, in agreement with other studies, the resulting drier conditions characterizing convection permitting RCMs likely arise from consistently longer (up to double) mean dry spell length compared to those from the simulations with parameterized convection. These findings shed light on how altered soil moisture-precipitation feedback can affect temperature extremes representation leading to ask at what extent heatwaves projected changes are dependent on the resolution considered.
How to cite: Sangelantoni, L. and Sobolowski, S.: Investigating the representation of heatwaves in km-scale simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6318, https://doi.org/10.5194/egusphere-egu21-6318, 2021.
Detailed long-term hydrometeorological dataset for Russian Arctic seas was created using hydrodynamic modelling via regional nonhydrostatic atmospheric model COSMO-CLM for 1980 – 2016 period with ~12 km grid. Many test experiments with different model options for summertime and wintertime periods were evaluated to determine the best model configuration. Verification has showed that optimal model setup included usage of ERA-Interim reanalysis as forcing data, new model version 5.05 with a so-called ICON-based physics and spectral nudging technique. Final long-term experiments were simulated on the MSU Supercomputer Complex “Lomonosov-2” become more than 120 Tb data volume excluding many side files.
Primary evaluation of obtained dataset was done for surface wind and temperature variables. There are some mesoscale details in wind sped climatology reproduced by COSMO-CLM dataset including the Svalbard, Severnaya Zemlya islands, and the western coast of the Novaya Zemlya island. At the same time, high wind speed frequencies based on COSMO-CLM data increased compared to ERA-Interim, especially over Barents Sea, Arctic islands (Novaya Zemlya) and some seacoasts and mainland areas. Regional details are manifested in wind speed increase and marked well for large lakes and orography (Taymyr and Kola peninsulas, Eastern Siberia highlands).
Comparison of two periods (1980 – 1990 and 2010 – 2016) has shown that spatial distributions of high wind speed frequencies are very similar, but there are some detailed differences. Wind speed frequencies above 20.8 m/s has been decreased in the last decade over the Novaya Zemlya, southwest from Svalbard, middle Siberia inlands; however, it has been increased over Franz Josef Land and Severnaya Zemlya.
Large-scale temperature climatology patterns have shown a good accordance between ERA-Interim and COSMO-CLM datasets. Significant temperature patterns are detailed relief and lakes manifestations, e.g., over Scandinavian mountains, Eastern Siberian and Taymyr highlands, Novaya Zemlya ranges. The added value in the 1% temperature percentile patterns is more pronounced, especially in the mountainous Eastern Siberia. Regional features are prominent over Onega and Ladoga lakes, and western Kara Sea. There is a remarkable warming over islands and Eastern Siberia valleys, and more clear temperature differentiation between ridges and valleys.
The nearest prospect of the COSMO-CLM Russian Arctic dataset application is its comparison with other appropriate datasets including reanalyses, satellite data, observations, etc. This will provide important and useful information about opportunities and restrictions of this dataset regarding different variables and specific regions, outline the limits of its applicability and get framework of possible tasks. The other important task is to share this dataset with scientific community.
How to cite: Platonov, V. and Varentsov, M.: COSMO-CLM Russian Arctic hindcast 1980 – 2016: experimental design and first evaluation results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6676, https://doi.org/10.5194/egusphere-egu21-6676, 2021.
Midlatitude western coastal regions are recognized as being important for the global energy cycle, marine and terrestrial biodiversity, and regional economies. These coastal regions exhibit a rich range of weather and climate phenomena, including persistent stratocumulus clouds, sea-breeze circulations, coastally-trapped Kelvin waves, and wind-driven upwelling. During the summer season, when impacts from transient synoptic systems are relatively reduced, the local climate is governed by a complex set of interactions among the atmosphere, land, and ocean. This complexity has so far inhibited basic understanding of the drivers of western coastal climate, climate variability, and climate change.
As a way of simplifying the system, we have developed a hierarchical regional climate model experimental framework focused on the western United States. We modify the International Centre for Theoretical Physics RegCM4 to use steady-state initial, lateral, and top-of-model boundary conditions: average July insolation (no diurnal cycle) and average meteorological state (winds, temperature, humidity, surface pressure). This July Base State simulation rapidly reaches a steady state solution that closely resembles the observed mean climate and the mean climate achieved using RegCM4 in a standard reanalysis-driven configuration. It is particularly notable that the near-coastal stratocumulus field is spatially similar to the satellite-observed stratocumulus field during arbitrary July days: including gaps in stratocumulus coverage downwind of capes. We run similar Base State simulations for the other calendar months and find that these simulations mimic the annual cycle. This suggests that the summer coastal stratocumulus field results from the steady-state response of the marine boundary layer to summertime climatological forcing; if true for the real world, this would imply that stratocumulus cloud fraction, within a given month, is temporally modulated by deviations from the summer base state (e.g., transient synoptic disturbances that interrupt the cloud field). We describe modifications to this simplified experimental framework aimed at understanding the factors that govern stratocumulus cloud fraction and its variability.
How to cite: O'Brien, T., Burkle, T., Krauter, M., and Trapp, T.: A Regional Climate Model Laboratory for Understanding Coastal Climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12832, https://doi.org/10.5194/egusphere-egu21-12832, 2021.
The western U.S. precipitation climatology simulated by the NA-CORDEX regional climate model ensembles are examined to evaluate the capability of the 0.44° and 0.22° resolutionensembles to reproduce 1) the annual and semi-annual precipitation cycle of several hydrologically important western U.S. regions and 2) localized seasonality in the amount and timing of precipitation. Collectively, when compared against observation-based gridded precipitation, NA-CORDEX RCMs driven by ERA-Interim reanalysis at the higher resolution 0.22° domain resolution dramatically outperformed the 0.44° ensemble over the 1950-2005 historical periods. Furthermore, the ability to capture the annual and semi-annual modes of variability was starkly improved in the higher resolution 0.22° ensemble. The higher resolution members reproduced more consistent spatial patterns of variance featuring lower errors in magnitude—especially with respect to the winter-summer and spring-fall seasonality. A great deal of spread in model performance was found for the semi-annual cycles, although the higher-resolution ensemble exhibited a more coherent clustering of performance metrics. In general, model performance was a function of which RCM was used, while future trend scenarios seem to cluster around which GCM was downscaled.
Future projections of precipitation patterns from the 0.22° NA-CORDEX RCMs driven by the RCP4.5 “stabilization scenario” and the RCP8.5 “high emission” scenario were analyzed to examine trends to the “end of century” (i.e. 2050-2099) precipitation patterns. Except for the Desert Southwest’s spring season, the RCP4.5 and RCP8.5 scenarios show a consensus change towards an increase in winter and spring precipitation throughout all regions of interest with the RCP8.5 scenario containing a greater number of ensemble members simulating greater wetting trends. The future winter-summer mode of variability exhibited a general consensus towards increasing variability with greatest change found over the region’s terrain suggesting a greater year-to-year variability of the region’s orographic response to the strength and location of the mid-latitude jet streams and storm track. Increasing spring-fall precipitation variability suggests an expanding influence of tropical moisture advection associated with the North American Monsoon, although we note that like many future monsoon projections, a spring “convective barrier” was also apparent in the NA-CORDEX ensembles.
How to cite: Meyer, J., Wang, S.-Y. (., Gillies, R., and Yoon, J.-H.: Evaluating the ability of NA-CORDEX to simulate the seasonal modes of precipitation variability across the Western United States: Does resolution matter?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6999, https://doi.org/10.5194/egusphere-egu21-6999, 2021.
Hindukush Karakorum and Himalayan (HKH) is a unique region with a vast number of glaciers and lies in the north of the South Asia landmass, which serves as the main reservoir for the South Asian freshwater resources. By using CORDEX-CORE downscaled simulations with ICTP Regional Climate Model (RegCM4.7) the climate change impact on the water resources of the HKH region is analysed. HKH contains Indus, Ganges and Brahmaputra water basins, which are feed from both snow as well as precipitation. Due to the temperature increase over this region, the snowmelt timing will be affected, and therefore the snowmelt driven runoff (SDR) in the whole HKH basin. This effect will be combined with the projected increase of precipitation and in particular convective precipitation mostly due to extreme precipitation increase. As a result for the whole HKH basin, the water year will be longer with a shift (negative) toward the earlier months of the year of the time when the 25th (~2-3 months), 50th( ~1month), and 75th (~1 month) percentile of the total runoff is observed in a certain point, in the upper part of the basin and a positive shift (~10 days) in the lower part of the basin for the 50th and 75th percentile. The results show that the Indus basin is the one most affected by the snow melt time change followed by the Brahmaputra and Ganges as the last one. This study indicates that changing climate may result in a shift in the discharge timing over the HKH region and this information may be crucial for planning the mitigation and adaptation actions like for example building dams, changing dam regulation options, and changing agriculture strategies.
How to cite: Shafeeq, W., Coppola, E., and Di Sante, F.: Impact of climate change on runoff timing over the Hindukush Karakorum Himalaya (HKH) region using CORDEX-CORE scenario simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7549, https://doi.org/10.5194/egusphere-egu21-7549, 2021.
Convection permitting regional climate models (CP-RCMs, typical horizontal resolution O(1-3km)) are currently state of the art when it comes to simulating regional climate. Their level of resolved spatial detail and realistic behaviour of for example summer convection is unprecedented. Consequently, impact modelers and even society at large have a strong interest in their products. However, because the computational demands of running such CP-RCMs are still huge, most of the simulations to date are relatively short, typically on the order of 10 years. Future trends are then derived from differences between two single time-slice experiments.
In contrast, conventional regional climate models (RCMs), that operate on typical “CORDEX” resolution (O(10km)), nowadays are relatively cheap to run, making it feasible to generate large ensembles of long transient integrations. These ensembles allow for a better determination of the amplitude of the internal variability and therefore come with higher signal-to-noise ratios. Invariably, it turns out that internal variability on the 10-year time scale (i.e., the typical time scale of the CP-RCM simulations) is considerable, if not very large for climate parameters like mean precipitation and temperature, let alone for climate extremes. This not only holds for the RCM results of course, but also for the CP-RCMs, perhaps even more strongly.
Two questions arise. First, to what extent are the mean trends derived from CP-RCM simulations meaningful given the large amplitude of internal variability at time scales used for the simulation? Second, how can we estimate the amplitude of internal variability at the 10-year time scale in the first place? We examine answers to these two basic questions in the GCM/RCM world where large ensembles are routinely available. The expectation is that some of the lessons learned here will carry over to the CP-RCM world.
How to cite: de Vries, H., Lenderink, G., and van der Wiel, K.: Estimating internal variability from relatively short regional-climate simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7986, https://doi.org/10.5194/egusphere-egu21-7986, 2021.
Extreme weather events, such as heavy precipitation, hail storms, heat waves, droughts and strong wind gusts have a detrimental impact on East African societies. The Lake Victoria Basin (LVB) is especially vulnerable, due to a large and growing population at risk from flooding. Moreover, nightly storms on the lake often catch fishermen by surprise. As the frequency and intensity of weather and climate extremes in the region is projected to further increase substantially with climate change, so do the risks. This has potentially major consequences for livelihoods and policy. The ultimate aim of the CORDEX Flagship Pilot Study ELVIC (Climate Extremes in the Lake Victoria Basin) is therefore to investigate how extreme weather events will evolve in the future in the LVB and to provide improved information to the impact community. ELVIC brings together different research groups that perform simulations with multiple high-resolution regional climate models operating at the convection-permitting scale (CPS) (https://ees.kuleuven.be/elvic). As a first step towards this overall goal, the added value of the CPS on the representation of deep convective systems in Equatorial Africa is assessed. For this purpose, 10-year present-day model simulations were carried out with five regional climate models at both parameterized and convection-permitting scales, namely COSMO-CLM, RegCM, AROME, WRF and MetUM .
Similarly to other regions in the world, there is no unanimous improvement nor deterioration in the representation of the spatial distribution of total rainfall and the seasonal cycle when going to the CPS. Moreover, substantial biases in the multi-annual averages (up to 30 W m-2) and seasonal cycle in Top-Of-Atmosphere (TOA) upward radiative fluxes remain, both in some models with parameterized and with explicitly resolved convection. Most substantial systematic improvements were found in the representation of the diurnal cycle in precipitation, the diurnal cycle in TOA radiation, some metrics for precipitation intensity and number of rain events. More specifically, the timing of the daily maximum in precipitation is systematically delayed when going to the CPS, thereby improving the agreement with observations. In particular, peaktime of precipitation strongly improves over land, especially at the shores of the lake, indicative of a better representation of the impact of the lake-land-mountain circulations on the convection at CPS. The underestimation in the 90th rainfall quantile of three-hourly precipitation in the parameterized models is alleviated. For the 95th and 99th percentile of precipitation no clear improvement nor deterioration is found, which might be related to poor observational constraints on extreme precipitation. The large overestimation in the total number of rainy events is alleviated when going to the CPS. The diurnal range in the radiative fluxes at the TOA strongly improves when going to CPS, especially for the longwave. All this indicates that the representation of the convective systems is strongly improved when going to CPS, giving confidence that the models are a valuable tool for studying how extreme precipitation events evolve in the future in the LVB.
How to cite: van Lipzig, N. P. M., Van de Walle, J., Thiery, W., Demuzere, M., Nikulin, G., Glazer, R., Coppola, E., Pinto, J. G., Fink, A. H., Ludwig, P., Rowell, D., Berthou, S., Finney, D., and Marsham, J.: Representation of precipitation and top-of-atmosphere radiation in a multi-model convection- permitting ensemble for the Lake Victoria Basin (East-Africa), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8376, https://doi.org/10.5194/egusphere-egu21-8376, 2021.
Downscaling data from General Circulation Models (GCMs) with Regional Climate Models (RCMs) is a computationally expensive process, even more so running at the convection permitting scale (CP). Despite the high-resolution products of these simulations, the Added Value (AV) of these runs compared to their driving models is an important factor for consideration. A new method was recently developed to quantify the AV of historical simulations as well as the Climate Change Downscaling Signal (CCDS) of forecast runs. This method presents these quantities spatially and thus the specific regions with the most AV can be identified and understood.
An analysis of daily precipitation from a 55-model EURO-CORDEX ensemble (at 12 km resolution) was assessed using this method. It revealed positive AV throughout the domain with greater emphasis in regions of complex topography, coast-lines, and the tropics. Similar CCDS was obtained when assessing the RCP 8.5 far future runs in these domains. This paper looks more closely at the CCDS obtained with this method and compares it to other climate change signals described in other studies.
The same method is now being applied to assess the AV and CCDS of daily precipitation from an ensemble of models at the CP scale (~3 km) over different domains within Europe. The current stage of the analysis is also looking into the AV of using hourly precipitation instead of daily.
How to cite: Ciarlo, J., Coppola, E., Pichelli, E., and Torres Alavez, J. A. and the FPS-Conv Team: Applying the new spatially distributed Added Value Index and Climate Change Downscaling Signal for Regional Climate Models to high-resolution EURO-CORDEX and convection permitting scale simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8849, https://doi.org/10.5194/egusphere-egu21-8849, 2021.
In the frame of the European Climate Prediction system (EUCP) H2020 project and COordinated Regional climate Downscaling Experiment (CORDEX), we have performed the ERA-Interim driven regional climate simulations with the coupled atmosphere (WRF)-land surface (ORCHIDEE) RegIPSL model at 20 km (EUR20; with parameterized convection) and 3 km (SWE3; convection-permitting/resolving) horizontal grid spacing over the Iberian Peninsula (IP) for the period of 2000-2009. The Iberian Peninsula is an area with a rich diversity of climates which is affected by several high impact extreme events such as droughts and flash floods for which the coupling processes between land surface and atmosphere play a key role. The aim of this first study is to evaluate the added value of the simulated mean and extreme precipitation in the convection-permitting simulation compared to the coarser resolution simulation for the four seasons (DJF, MAM, JJA, and SON). Experiment is performed as a chain of simulations while the EUR20 simulation is forced by the 6-hourly ERA-Interim initial and lateral boundary conditions (IC-LBCs) and the SWE3 simulation is forced by the 3-hourly EUR20 simulated IC-LBCs. The SPREAD (5 km) and Iberia01 (10 km) high-resolution daily gridded mean precipitation have been used as reference datasets for the validation of the simulated precipitation.
We have not found any consistent improvement in the SWE3 simulation compared to the parent EUR20 simulation for the seasonal mean precipitation of the IP except the spatial variation over mountainous peaks. The analysis shows a lack of mean precipitation in the western and southern parts of the domain in the SWE3 which explains that on average over the whole domain, the spatial-temporal pattern of the observed mean precipitation is quantitatively better represented by the EUR20 than the SWE3 simulation. The added value of kilometer scale simulation over the driving coarser scale simulation is obtained at various indices; in the representation of the spatial-temporal distribution of the Kolmogorov-Smirnov (K-S) distance, wet-day frequency and intensity for each season at both resolutions i.e. downscaled (3km) and upscaled (20km), although the SWE3 simulation slightly underestimates the observed frequency and intensity of the wet-day precipitation. The improvement of finer scale simulation over the coarser resolution simulation has also been found in the spatial-temporal distribution of the heavy precipitation events. It has also been noted that the spatial-temporal distribution of precipitation for all metrics used varies slightly between the two observation datasets for all seasons, and it may be due to the different resolution of both datasets. The absence of sub-daily observed datasets did not allow us to further investigate the added value of the convective permitting simulation at hourly time scales, but we also noticed heavier hourly precipitation and a shift in the diurnal cycle. These results demonstrate a clear advantage of using a RegIPSL model at the kilometric scale over the IP in simulation for high impact weather events, consistently with previous studies over other areas. Further analysis will be done on the hydrological processes in response to these shifts of precipitation distribution between the two simulations.
How to cite: Shahi, N. K., Polcher, J., Bastin, S., Pennel, R., and Fita, L.: Assessment of the spatial variability of the added value on precipitation of convection-permitting simulation over the Iberian Peninsula using the RegIPSL regional earth system model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9062, https://doi.org/10.5194/egusphere-egu21-9062, 2021.
On the evening on July 2, 2011 a severe cloud burst occurred in the Copenhagen area. During the late afternoon deep moist convection developed over nearby Skåne (the southernmost part of Sweden) in an airstream from east-northeast. In the early evening the DMC passed over Øresund to Copenhagen, where it created a severe flash flood. Between 90 and 135 mm of precipitation in less than 2 hours was recorded ooding cellars, streets, and key roads. The deluge caused 6 billion Danish kroner in damage. Although that such extreme events are rare, the impacts on society is important and should be understood under a warmer climate. Although regional climate models have recently reached the convection permitting resolution, reproducing such events is still challenging.
Several studies suggest that extreme precipitations should increase under a future warmer climate using transient simulation or a pseudo-warming approach. It is still unclear how such event would behave under warmer or colder synoptic conditions. Using a forecast-ensemble method, but keeping a climate perspective, this study assesses the risk rising from such an event under otherwise almost identical, but warmer or colder conditions. With this set-up, we find that the development of the system that resulted in observed downpour exhibit quite a sensitivity to the initial conditions and contrary to a linear thinking, the risk of flooding is decreasing as the climate warms due to the inhibition of the CAPE by the additional lapse-rate anomalies used in this study. We therefore propose that the PGW method should be used with caution and that extreme precipitation events also in transient simulations of future climates need to be studied in detailed to address the limitations to models ability to produce those most extreme and by nature inherently rare events.
How to cite: Matte, D., H. Christensen, J., Fedderson, H., A. Pederson, R., Vedel, H., and Woetmann Nielsen, N.: When the trigger of deep convection gets tricky in idealized climate simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9497, https://doi.org/10.5194/egusphere-egu21-9497, 2021.
Extreme weather events represent one of the most visible and immediate hazards to society. Many of these types of phenomena are projected to increase in intensity, duration or frequency as the climate warms. Of these extreme winds are among the most damaging historically over Europe yet assessments of their future changes remain fraught with uncertainty. This uncertainty arises due to both the rare nature of extreme wind events and the fact that most model are unable to faithfully represent them. Here we take advantage of a 15-member ensemble of high-resolution Euro-CORDEX simulations (~12km) and investigate projected changes in extreme winds using a peaks-over-threshold approach. Additionally, we show that - despite lingering model deficiencies and inadequate observational coverage - there is clear added value of the higher resolution simulations over coarser resolution counterparts. Further, the spatial heterogeneity and highly localized nature is well captured. Effects such as orographic interactions, drag due to urban areas, and even individual storm tracks over the oceans are clearly visible. As such future changes also exhibit strong spatial heterogeneity. These results emphasize the need for careful case-by-case treatment of extreme wind analysis, especially when done in a climate adaptation or decision-making context. However, for more general assessments the picture is clearer with increases in the return period (i.e., more frequent) extreme episodes projected for Northern, Central and Southern Europe throughout the 21st century. While models continue to improve in their representation of extreme winds, improved observational coverage is desperately needed to better constrain and obtain more robust assessments of future extreme winds over Europe and elsewhere.
How to cite: Sobolowski, S. and Outten, S.: Extreme wind projections over Europe in the high-resolution Euro-CORDEX ensemble, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9666, https://doi.org/10.5194/egusphere-egu21-9666, 2021.
The European Regional Development Fund-Project BigData@Geo aims to create highly resolved climate projections for the model region of Lower Franconia in Bavaria, Germany. These projections are analyzed and made available to local stakeholders of agriculture, forestry, and viniculture as well as general public. Since regional climate models’ spatiotemporal resolution often is too coarse to deal with such local issues, the regional climate model REMO is improved within the frame of the project in cooperation with the Climate Service Center Germany (GERICS).
Accurate and highly resolved climate projections require realistic modeling of soil hydrology. Thus, REMO’s original bucket scheme is replaced by a 5-layer soil scheme. It allows for the representation of water below the root zone. Evaporation is possible solely from the top layer instead of the entire bucket and water can flow vertically between the layers. Consequently, the properties and processes change significantly compared to the bucket scheme. Both, the bucket and the 5-layer scheme, use the improved Arno scheme to separate throughfall into infiltration and surface runoff.
In this study, we examine if this scheme is suitable for use with the improved soil hydrology or if other schemes lead to better results. For this, we (1) modify the improved Arno scheme and further introduce the infiltration equations of (2) Philip as well as (3) Green and Ampt. First results of the comparison of these four different schemes and their influence on soil moisture and near-surface atmospheric variables are presented.
How to cite: Abel, D., Ziegler, K., Pollinger, F., and Paeth, H.: Comparison of different infiltration schemes in the regional climate model REMO, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9874, https://doi.org/10.5194/egusphere-egu21-9874, 2021.
A large uncertainty exists today in quantifying the absorbing aerosol snow darkening effects, especially at the regional scale. It is considered as one of the main factors contributing to snow melting and glacier retreat over the Himalayas-Tibetan Plateau (HTP). Using International Centre for Theoretical Physics (ICTP)’s regional climate model - RegCM4 coupled with SNow, ICe and Aerosol Radiation (SNICAR) embedded within Community Land Model (CLM4.5), we examine the possible changes induced by aerosol deposition over the HTP and its dynamical impacts over northern India during the pre-monsoon season, which is critical for the inception and development of the monsoon. Sensitivity experiments without (DRE) and with aerosol snow darkening effects (SDDRE) were carried out over the South Asia - Coordinated Regional Climate Downscaling Experiment (CORDEX) domain for the period 2005-2010. It is found that there is a significant reduction of snow fraction by 10 to 25 % and an increase in surface temperatures (> 4° C) in SDDRE, which improves the model performance when comparing against observations. This response is dominated by a larger portion of dust deposition compared to black carbon. The associated increase in the surface and tropospheric temperature over HTP draws in dry air from central and west Asia towards northern India leading to a decrease in the precipitation in SDDRE. The increase in the northwesterly winds also modulates the dust cycle by enhancing dust emissions over the Thar Desert as well as the columnar burden and depositional fluxes over northern India. As a result of the decrease in precipitation, surface temperature increases and generates a low-pressure system over northern India, which further strengthens the dust transport and partially contributes to the occurrence of dust storms. We also find that the snow darkening effect induces an earlier monsoon onset due to larger temperature gradients initiated over the HTP. Some analysis of precipitation and temperature extremes as well as limitations will be presented. Our study provides evidence that the aerosol snow darkening effects could have substantial impacts over HTP as well as over northern India through feedbacks and hence needs to be considered in climate simulations.
How to cite: Das, S., Coppola, E., Panicker, A. S., and Gautam, A. S.: Linkage between the absorbing aerosol snow darkening effects over the Himalayas-Tibetan Plateau and the pre-monsoon climate over northern India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10308, https://doi.org/10.5194/egusphere-egu21-10308, 2021.
This study aims to evaluate how extreme winds (above the 95th percentile) are represented in a downscaling using the regional model WRF over the CORDEX South American domain in an approximate 25 km (0.22 degrees) horizontal resolution, along with CFSR as input. The main focus of the analysis resides over the coastal Brazilian region, given a large number of offshore structures from oil and gas industries subject to impact by severe events. Model results are compared with a reanalysis product (ERA5), estimates from satellites product (Cross-Calibrated Multi-Platform Wind Speed), and available buoy data (Brazilian National Buoy Project). Downscaling results from WRF show an underestimation of maximum and extreme wind speeds over the region when compared to all references, along with overestimation in the continental areas. This directly impacts results for extreme value estimation for a larger return period and severity evaluation of extreme wind events in future climate projections. To address this, a correction procedure based on the linear relationship between severe wind from satellite and model results is applied. After linearly corrected, the extreme and maximum wind speed values increase and errors in the representation of severe events are reduced in the downscaling results.
How to cite: Silva, N. P. D., Rocha, R. P. D., Crespo, N. M., de Camargo, R., Lima, J. A. M., Kaufmann, C. L. G., and Andrioni, M.: Extreme winds in a WRF downscaling for the SAM-22 CORDEX domain for the 1979-2018 Historical Period, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10363, https://doi.org/10.5194/egusphere-egu21-10363, 2021.
The world needs energy for its social and economic development. In the growing population and industrialization, there is an increasing demand for energy worldwide. The fossil fuel resources are still major resources for fulfilling this energy demand though they are responsible for the increased GHG emissions. Renewable energy is an alternative and greener approach towards meeting increasing energy demand. The wind energy is one of the most prominent resources of greener and renewable energy. The islands of Mauritius and Reunion in the southwest Indian Ocean are blessed with wind resources. The wind energy can be used to meet the demand of energy requirement of these two islands by increasing the number of wind turbines. However, energy generation with wind turbines is sensitive to the variability in the surface wind due to climate variability. The surface wind data available is sparse due to limited ground-based observation. The data quality is also affected by instrumental errors, and data is available only for past and present. Regional Climate Models (RCMs) are the main source of climate information for the present and the future. However, simulations from RCMs deal with biases from various sources and therefore need to bias-corrected. Here we use a transfer function based on the method proposed by Li et al. (2010) for the bias-correction of surface wind over Reunion and Mauritius islands. For this purpose, RegCM4.7 RCM from CORDEX AFR22 domain has been chosen for the time period of 1981-2004. The data is interpolated at 9 km resolution and bias-corrected with respect to surface wind data obtained from ERA5 land reanalysis data. The bias-corrected results are validated with the ERA5 land reanalysis data set.
How to cite: Singh, S., Tang, C., and Morel, B.: Bias-correction of Surface Wind over Reunion and Mauritius Islands using CORDEX Regional Climate Model: RegCM4.7, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10975, https://doi.org/10.5194/egusphere-egu21-10975, 2021.
The evolution of temperature, precipitation and snow cover in the European Alps have been simulated with the regional climate model MAR applied with a 7 kilometre horizontal resolution and driven by the ERA-20C (1902-2010) and the ERA5 reanalyses (1981-2018). A comparison with observational datasets, including French and Swiss local meteorological stations, in-situ glacier mass balance measurements and reanalysis product demonstrates high model skill for snow cover duration and snow water equivalent (SWE) as well as for the climatology and the inter-annual variability of both temperature and precipitation. The relatively high resolution allows to estimate the meteorological variables up to 3000m.a.s.l. The vertical gradient of precipitation simulated by MAR over the European Alps reaches 33% km-1 (1.21 mmd-1.km-1) in summer and 38%km-1 (1.15mmd mmd-1.km-1) in winter, on average over 1971–2008 and shows a large spatial variability. This study evidences seasonal and altitudinal contrasts of climate trends over the Alps. A significant (pvalue< 0.05) increase in mean winter precipitation is simulated in the northwestern Alps over 1903–2010, with changes typically reaching 20% to 40% per century, a signal strongly modulated by multi-decadal variability during the second part of the century. A general drying is found in summer over the same period, exceeding 20% to 30% per century in the western plains and 40% to 50% per century in the southern plains surrounding the Alps but remaining smaller (<10%) and not significant above 1500ma.s.l. Over 1903–2010, the maximum of daily precipitation (Rx1day) shows a general and significant increase at the annual timescale and also during the four seasons, reaching local values between 20% and 40% per century over large parts of the Alps and the Apennines. Trends of Rx1day are significant (pvalue<0.05) only when considering long time series, typically 50 to 80 years depending on the area considered. Some of these trends are nonetheless significant when computed over 1970–2010, suggesting a recent acceleration of the increase in extreme precipitation. Rx1day increase occurs where the annual correlation between temperature and intense precipitation is high. The highest warming rates in MAR are found at low elevations (< 1000 m a.s.l) in winter, whereas they are found at high elevations (> 2000 m a.s.l) in summer. In spring, warming trends show a maximum at intermediate elevations (1500 m to 1800 m). Our results suggest that higher warming at these elevations is mostly linked with the snow-albedo feedback in spring and summer.
How to cite: Ménégoz, M., Beaumet, J., Gallée, H., Fettweis, X., Morin, S., Blanchet, J., Six, D., Vincent, C., Jourdain, N. C., Wilhelm, B., and Anquetin, S.: Contrasting seasonal changes in temperature, precipitation and snow cover simulated over the European Alps during the twentieth century, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11097, https://doi.org/10.5194/egusphere-egu21-11097, 2021.
We here present a climate study on Heavy Precipitation Events (HPEs). To this aim we use an ensemble of convection-permitting regional climate models on a domain that covers the alps and large parts of the Mediterranean. These HPEs are generally meso-scale convective systems, which often are related to a landfall or orographic blocking. For society they are of major interest as they may damage infrastructure and threaten lives through flash floods and strong winds.
From the models' output of precipitation we identify HPEs by applying an well-established clustering and tracking algorithm (MET MTD).
Our study is organized into an evaluation and a climate study part. We evaluate the models by comparison of the evaluation scenario, driven by reanalysis data, against observations. In order to evaluate the tracking algorithm we analyse three specific historic events, occurring in southern France, central Italy and Germany. Eventually we investigate the climate response by comparison of the far future projection (2090-2100) under the rcp85 forcing against the historical scenario (1996-2006).
In regards of the model evaluation we find that the annual cycle is very well captured by model ensemble, although the models overestimate HPEs over orography and underestimated HPEs over flatter terrain.
Concerning the climate response our main result highlights that precipitation associated with HPEs is increasing in the far future, even though total annual precipitation is decreasing. Overall more HPEs occur in the far future, but only for an extended winter season (October to April), while for months May to September the occurrence of HPEs is decreasing. This behaviour motivates us to investigate the annual cycle of HPEs in greater detail.
How to cite: Müller, S., Pichelli, E., Coppola, E., Berthou, S., Brienen, S., Caillaud, C., Dobler, A., and Tölle, M.: The Climate Response of Heavy Precipitation Events over the Alps and in the Mediterranean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11138, https://doi.org/10.5194/egusphere-egu21-11138, 2021.
Explosive cyclones (ECs) are extratropical systems, often associated with extreme events, which experience a fast deepening (~24 hPa/24 h) over a relatively short time range. Here, we analyze changes in the austral winter characteristics of ECs in three domains (Africa-AFR, Australia-AUS and South America-SAM) as projected by Regional Climate Model (RegCM4) under RCP8.5 emission scenario in the CORDEX-CORE framework. RegCM4 was nested in three global climate models (GCMs) from CMIP5 (HadGEM2-ES, MPI-ESM-MR and NorESM-1M) and executed with 25 km of grid spacing. The cyclone database was obtained with the application of an automatic detection and tracking scheme to the 6-hourly mean sea level pressure fields. Extratropical cyclones with explosive features are then selected using the Sanders and Gyakum criterium. Following IPCC recommendation, we analyze the reference 1995–2014 period and the end-of-century 2080–2099 period. ECs represent ~13-17% of the total number of cyclones in ERA-Interim reanalysis during the austral winter, while the simulation ensembles, in general, underestimate this value. While in the AFR domain GCMs ensemble represents better the percentage of ECs compared to ERA-Interim, in AUS and SAM domains RegCM4 has a better performance than GCMs. The percentage of ECs compared to the total number of cyclones in each domain is projected to increase, with higher positive trends for the SAM domain (7.4% in GCMs and 5.6% in RegCM4) than AFR (3.3% in GCMs and 3.9% in RegCM4) and AUS (3.9% in GCMs and 1.7% in RegCM4). Compared to the present climate, ECs in the future will be stronger and faster but with a shorter lifetime.
How to cite: Reboita, M., Machado Crespo, N., Reale, M., Torres, J. A., and Porfírio da Rocha, R.: Explosive Cyclones in the CORDEX-CORE projections for Southern Hemisphere domains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11746, https://doi.org/10.5194/egusphere-egu21-11746, 2021.
Urban areas are prone to climate change impacts. A transition towards sustainable and climate-resilient urban areas is relying heavily on useful, evidence-based climate information on urban scales. However, current climate data and information produced by urban or climate models are either not scale compliant for cities, or do not cover essential parameters and/or urban-rural interactions under climate change conditions. Furthermore, although e.g. the urban heat island may be better understood, other phenomena, such as moisture change, are little researched. Our research shows the potential of regional climate models, within the EURO-CORDEX framework, to provide climate projections and information on urban scales for 11km and 3km grid size. The city of Berlin is taken as a case-study. The results on the 11km spatial scale show that the regional climate models simulate a distinct difference between Berlin and its surroundings for temperature and humidity related variables. There is an increase in urban dry island conditions in Berlin towards the end of the 21st century. To gain a more detailed understanding of climate change impacts, extreme weather conditions were investigated under a 2°C global warming and further downscaled to the 3km scale. This enables the exploration of differences of the meteorological processes between the 11km and 3km scales, and the implications for urban areas and its surroundings. The overall study shows the potential of regional climate models to provide climate change information on urban scales.
How to cite: Langendijk, G. S., Rechid, D., and Jacob, D.: Future humidity extremes in an urban-rural context - using regional climate model projections down to convection permitting scales for Berlin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12054, https://doi.org/10.5194/egusphere-egu21-12054, 2021.
Land-atmosphere energy and water exchanges are fundamentally linked to soil-moisture. The distribution of the planets’ biomes hinges on the surface-atmosphere coupling since soil moisture and temperature feedbacks have a strong influence on plant transpiration and photosynthesis. Land use/land cover changes (LUC) modify locally land surface properties that control the land-atmosphere mass, energy, and momentum exchanges. The impact of these changes depends on the scale and nature of land cover modifications and is very difficult to quantify. However, large inconsistencies in the LUC impacts are observed between models, highlighting the need for common LUC across a large ensemble of models. The Flagship Pilot Study LUCAS (Land Use & Climate Across Scales) provides a coordinated effort to study LUC using an ensemble of regional climate models (RCMs). In the first phase of the project 3 experiments were performed for continental Europe: EVAL (current climate); GRASS (trees replaced by grassland) and FOREST (grasses and shrubs replaced by trees). An analysis of the energy and moisture balance for the three experiments is performed, focusing on the relationship between the fluxes partitioning, heat waves and droughts. To better asses the link between extreme temperatures and soil moisture or evapotranspiration, a new coupling metric for short time scales is proposed, the Latent Heat Flux-Temperature Coupling Magnitude (LETCM). This new metric is computed for a specific period, considering the positive temperature extremes and the negative latent heat flux extremes. Areas with positive magnitude values imply higher temperature anomaly, due to a negative latent heat flux anomaly. This new metric only considers periods of strong coupling, with positive signals in areas of high temperatures and evaporative stress, allowing for the detection of events that are extreme for energy and water cycle. Concurrently, a new decile based normalised drought index is used to examine the concurrent heat extremes and droughts. The analysis focuses on the three experiments revealing that the number, amplitude and spatial distribution of compound extreme heat and drought is highly model dependant. The impact of afforestation or deforestation is not consistent across models.
The authors wish to acknowledge project LEADING (PTDC/CTA-MET/28914/2017) and FCT - project UIDB/50019/2020 - Instituto Dom Luiz.
How to cite: Cardoso, R. M., Lima, D. D. C. A., Soares, P. M. M., Rechid, D., Breil, M., Coppola, E., Davin, E., Hoffmann, P., Jach, L., Katragkou, E. K., Meier, R., Mooney, P. A., de Noblet-Ducoudré, N., Panitz, H.-J., Sofiadis, I., Strada, S., Strandberg, G., Tölle, M., and Warrach-Sagi, K.: Land-atmosphere coupling during compound extreme heat and drought events in the LUCAS experiment: a new coupling metric for climate extremes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15797, https://doi.org/10.5194/egusphere-egu21-15797, 2021.
Everyone, politicians, public administrations, business owners, and citizens want to know how climate changes will affect them locally. Having such knowledge offers everyone the opportunity to make informed choices and take action towards mitigation and adaptation.
In order to develop locally relevant climate service products and climate advisory services, as we do at GERICS, we must extract localized climate change information from Regional Climate Model ensemble simulations.
Common challenges associated with developing such services include the transformation of petabytes of data from physical quantities such as precipitation, temperature, or wind, into user-applicable quantities such as return periods of heavy precipitation, e.g. for legislative or construction design frequency. Other challenges include the technical and physical barriers in the use and interpretation of climate data, due to large data volume, unfamiliar software and data formats, or limited technical infrastructure. The interpretation of climate data also requires scientific background knowledge, which limit or influence the interpretation of results.
These barriers hinder the efficient and effective transformation of big data into user relevant information in a timely and reliable manner. To enable our society to adapt and become more resilient to climate change, we must overcome these barriers. In the Helmholtz funded Digital Earth project we are tackling these challenges by developing a Climate Change Workflow.
In the scope of this Workflow, the user can easily define a region of interest and extract the relevant climate data from the simulations available at the Earth System Grid Federation (ESGF). Following which, a general overview of the projected changes, in precipitation for example, for multiple climate projections is presented. It conveys the bandwidth, i.e. the minimum/maximum range by an ensemble of regional climate model projections. We implemented the sketched workflow in a web-based tool called The Climate Change Explorer. It addresses barriers associated with extracting locally relevant climate data from petabytes of data, in unfamilar data formats, and deals with interpolation issues, using a more intuitive and user-friendly web interface.
Ultimately, the Climate Change Explorer provides concise information on the magnitude of projected climate change and the range of these changes for individually defined regions, such as found in GERICS ‘Climate Fact Sheets’. This tool has the capacity to also improve other workflows of climate services, allowing them to dedicate more time in deriving user relevant climate indicies; enabling politicians, public administrations, and businesses to take action.
How to cite: Nam, C., Tiedje, B., Pfeifer, S., Rechid, D., and Eggert, D.: Climate Change Explorer: Extracting localized data for developing Climate Services, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12336, https://doi.org/10.5194/egusphere-egu21-12336, 2021.
The impact of climate change on precipitation over Southern Africa is of particular interest due to its possible devastating societal impacts. To add to this, simulating precipitation is challenging and models tend to show strong biases over this region, especially during the Austral Summer (DJF) months. One of the reasons for this is the mis-representation of the Angolan Low (AL) and its influence on Southern Africa’s Summer precipitation in the models. Therefore, this study aims to explore and compare different models’ ability to capture the AL and its link to precipitation variability as well as consider the impact climate change may have on this link. We also explore how the interaction between ENSO, another important mode of variability for precipitation, and the Angolan Low, impact precipitation, how the models simulate this and whether this could change in the future under climate change.
We computed the position and strength of the AL in reanalysis data and compared these results to three different model ensembles with varying resolutions. Namely, the CORDEX-CORE ensemble (CCORE), a new phase of CORDEX simulations with higher resolutions (0.22 degrees), the lower resolution (0.44 degrees) CORDEX-phase 1 ensemble (C44) and the CMIP5 models that drive the two RCM ensembles. We also used Self Organizing Maps to group DJF yearly anomaly patterns and identify which combination of ENSO and AL strength scenarios are responsible for particularly wet or dry conditions. Regression analysis was performed to analyze the relationships between precipitation and the AL and ENSO. This analysis was repeated for near (2041-2060) and far (2080-2099) future climate and compared with the present to understand how the strength of the AL, and its connection to precipitation variability and ENSO, changes in the future.
We found that, in line with previous studies, models with stronger AL tend to produce more rainfall. CCORE tends to simulate a stronger AL than C44 and therefore, higher precipitation biases. However, the regression analysis shows us that CCORE is able to capture the relationship between precipitation and the AL strength variability as well as ENSO better than the other ensembles. We found that generally dry rainfall patterns over Southern Africa are associated with a weak AL and El Nino event whereas wet rainfall patterns occur during a strong AL and La Nina year. While the models are able to capture this, they also tend to show more neutral ENSO conditions associated with these wet and dry patterns which possibly indicates less of a connection between AL strength and ENSO than seen in the observed results. Analysis of the future results indicates that the AL weakens, this is shown across all the ensembles and could be a contributing factor to some of the drying seen. These results have applications in understanding and improving model representation of precipitation over Southern Africa as well as providing some insight into the impact of climate change on precipitation and some of its associated dynamics over this region.
How to cite: Abba-Omar, S., Raffaele, F., Coppola, E., Jacob, D., Teichmann, C., and Remedio, A.: Representation of the Angolan low and Southern African Summer Precipitation in the CORDEX and CMIP5 models. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12531, https://doi.org/10.5194/egusphere-egu21-12531, 2021.
The interaction between climate variability, extreme events and societies in the Eastern Mediterranean and the Middle East (EMME) and the Nile river basin is of particular interest in the last 2000 years. Major civilizations and complex pre-modern societies have written the greatest and multifaceted history of the area. However, the influence of climate on the societies is examined only from the proxy records perspective, without the detail of the processes that offer regional climate model simulations. The present and future climate and climate variability of this region are currently studied in the frame of the MENA CORDEX program with different global and regional climate models. For the past climate, exist only global climate or earth system model simulations with a coarse spatial resolution with a minimum of 100 km horizontal resolution. We aim at improving our understanding of past climate in the EMME and the Nile river basin (Nile) at the regional scale and use an adjusted paleoclimate version of the COSMO-CLM. Test simulations have been performed over the study region for the years 2017-2018 to identify the best settings of CCLM with respect to the CORDEX-MENA simulations which are carried out by Bucchignani et al. (2016). Test simulations show the CCLM can correctly simulate large tropical volcanic eruptions, as conditions similar to the Tambora eruption by adapting the stratospheric aerosol optical depth (AOD) mimicking conditions after a Tambora-like volcanic eruption. In agreement with Bucchignani et al. (2016), the albedo and aerosols parameters are found to be most important for the area and may be responsible for larger deviations compared to observational data. Thus, CCLM climate modelling for the present (1979-2019) and selected paleo-periods (525-575 CE and 1220-1290 CE) with intense volcanic activity will be forced by the MPI-ESM-LR ‘past2k’ simulation with the optimized settings which is identified in the test simulations. Orbital, solar and volcanic forcing, together with vegetation, land-use changes and greenhouse gas changes will be addressed step by step in the CCLM with resolutions of 0.44° and 0.11°. The present-day simulations show that the temperature and precipitation are well simulated compare to reanalysis and observational data in general. Additional, CCLM correctly captured convection and cloud cover clearly define the model performance in the greater southern areas of the domain that are affected by the tropical convection. Further, the orography and the land-sea interaction seem to significantly influence the local climate and may lead to differences compared to observations, which may also be strongly connected with the specific spatial resolution. For example, the Ethiopian Highlands and the East African Plateau have high elevations and have a large impact on the regional climate.
Bucchignani, E., Cattaneo, L., Panitz, HJ. et al. Sensitivity analysis with the regional climate model COSMO-CLM over the CORDEX-MENA domain. Meteorol Atmos Phys 128, 73–95 (2016). https://doi.org/10.1007/s00703-015-0403-3
How to cite: Zhang, M., Hartmann, E., Xoplaki, E., and Wagner, S.: Regional paleoclimate in the EMME and the Nile basin based on COSMO-CLM with orbital and volcanic forcing at the different spatial resolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12545, https://doi.org/10.5194/egusphere-egu21-12545, 2021.
Southern South America (SSA) is a wide populated region exposed to extreme rainfall events, which are recognised as some of the major threats in a warming climate. These events produce large impacts on socio-economic activities, energy demand and health systems. Hence, studying this phenomena requires high-quality and high-resolution observational data and model simulations. In this work, the main features of daily extreme precipitation and circulation types over SSA were evaluated using a 4-model set of CORDEX regional climate models (RCMs) driven by ERA-Interim during 1980-2010: RCA4 and WRF from CORDEX Phase 1 and RegCM4v7 and REMO2015 from the brand-new CORDEX-CORE simulations. Observational uncertainty was assessed by comparing model outputs with multiple observational datasets (rain gauges, CHIRPS, CPC and MSWEP).
The inter-comparison of extreme events, characterized in terms of their intensity, frequency and spatial coverage, varied across SSA exhibiting large differences among observational datasets and RCMs, pointing out the current observational uncertainty when evaluating precipitation extremes, particularly at a daily scale. The spread between observational datasets was smaller than for the RCMs. Most of the RCMs successfully captured the spatial pattern of extreme rainfall across SSA, reproducing the maximum intensities in southeastern South America (SESA) and central and southern Chile during the austral warm (October to March) and cold (April to September) seasons, respectively. However, they often presented overestimations over central and southern Chile, and more variable results in SESA. RegCM4 and WRF seemed to well represent the maximum precipitation amounts over SESA, while REMO showed strong overestimations and RCA4 had more difficulties in representing the spatial distribution of heavy rainfall intensities. Focusing over SESA, differences were detected in the timing and location of extremes (including the areal coverage) among both observational datasets and RCMs, which poses a particular challenge when performing impact studies in the region. Thus, stressing that the use of multiple datasets is of key importance when carrying out regional climate studies and model evaluations, particularly for extremes.
The synoptic environment was described by a classification of circulation types (CTs) using Self-Organizing Maps (SOM) considering geopotential height anomalies at 500 hPa (Z500). Specific CTs were identified as they significantly enhanced the occurrence of extreme rainfall events in sectorized areas of SESA. In particular, a dipolar structure of Z500 anomalies that produced a marked trough at the mid-level atmosphere, usually located east of the Andes, significantly favoured the occurrence of extreme precipitation events in the warm season. The RCMs were able to adequately reproduce the SOM frequencies, although simplifying the predominant CTs into a reduced number of configurations. They appropriately reproduced the observed extreme precipitation frequencies conditioned by the CTs and their atmospheric configurations, but exhibiting some limitations in the location and intensity of the resulting precipitation systems.
In this sense, continuous evaluations of observational datasets and model simulations become necessary for a better understanding of the physical mechanisms behind extreme precipitation over the region, as well as for its past and future changes in a climate change scenario.
How to cite: Olmo, M. E. and Bettolli, M. L.: Precipitation extremes over southern South America and their synoptic environment in a set of CORDEX regional climate models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12582, https://doi.org/10.5194/egusphere-egu21-12582, 2021.
Using high-spatial-resolution regional simulations from the global program, Coordinated Regional Climate Downscaling Experiment-Coordinated Output for Regional Evaluations (CORDEX-CORE), we examine the capability of regional climate models (RCMs) to represent the El Niño–Southern Oscillation (ENSO) precipitation and surface air temperature teleconnections during boreal winter (December-February). This study uses CORDEX-CORE simulations for the period 1975-2004 with two RCMs, the RegCM4 and REMO, driven by three General Circulation Models (GCMs) from phase 5 of the Coupled Model Inter-comparison Project (CMIP5). The RCM simulations were run at a 25-km grid spacing over Africa, Central and North America, South Asia and South America.
The teleconnection patterns are calculated in the reanalysis data (observations), and these results are compared to those of the ensemble and individual simulations of both the GCM and RCM. Linear regression is used to calculate the teleconnection patterns and a permutation test is applied to calculate the statistical significance of the regression coefficients. Results show that overall, the ENSO signal from the GCMs is preserved in the ensemble and the individual RCM simulations over most of the regions analyzed. These reproduced most of the observed regional responses to ENSO forcing and showing teleconnection signals statistically significant at the 95% level. Furthermore, in some cases, the ensemble and individual simulations of RCMs improve the spatial pattern and the amplitude of the ENSO precipitation response of the GCMs, particularly over southern Africa, the Arabian-Asian region, and the region composed of Mexico and the southern United States. These results show the potential value of the GCM-RCM downscaling systems not only in the context of climate change research but also for seasonal to annual prediction.
How to cite: Torres-Alavez, A., Kucharski, F., Coppola, E., and Castro, L.: ENSO teleconnections in an ensemble of CORDEX-CORE regional simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13131, https://doi.org/10.5194/egusphere-egu21-13131, 2021.
During the last three decades significant trends compatible with a changing climate due to increased anthropogenic emissions have been observed. Changes are remarkable not only at global but also at regional scales. The Euro-Mediterranean sector has been identified as one of the hot spots potentially subject to critical impacts of climate change already manifest. In this work several long continuous (non re-initialized) WRF simulations at a high resolution (9 km) over peninsular Iberia that make use of a set of different land surface schemes have been performed. In doing so we categorize the impact of using alternate land surface models in long (30 years) continuous simulations since only such running approach allows to preserve the memory of the soil processes. Thus, we explore changes in the soil moisture content aiming at the detection of plausible evidences of drying trends, specially for the south of Spain. In addition we investigate a 30-year climatology of wind speed in the search of a potential stilling phenomenon already documented over several European and worldwide regions.
How to cite: García-Bustamante, E., González-Rouco, J. F., Navarro, J., Palomares Losada, A., García-García, A., Cuesta-Valero, F. J., and Beltrami, H.: Sensitivity of wind and soil moisture to the land surface component in 30-year continuous simulations over the Iberian Peninsula, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14345, https://doi.org/10.5194/egusphere-egu21-14345, 2021.
In this study, we evaluate a set of high-resolution (25–50 km horizontal grid spacing) global climate models (GCMs) from the High-Resolution Model Intercomparison Project (HighResMIP), developed as part of the EU-funded PRIMAVERA (Process-based climate simulation: Advances in high resolution modelling and European climate risk assessment) project, and from the EURO-CORDEX (Coordinated Regional Climate Downscaling Experiment) regional climate models (RCMs) (12–50 km horizontal grid spacing) over a European domain. It is the first time that an assessment of regional climate information using ensembles of both GCMs and RCMs at similar horizontal resolutions has been possible. The focus of the evaluation is on the distribution of daily precipitation at a 50 km scale under current climate conditions. Both the GCM and RCM ensembles are evaluated against high-quality gridded observations in terms of spatial resolution and station density. We show that both ensembles outperform GCMs from the 5th Coupled Model Intercomparison Project (CMIP5), which cannot capture the regional-scale precipitation distribution properly because of their coarse resolutions. PRIMAVERA GCMs generally simulate precipitation distributions within the range of EURO-CORDEX RCMs. Both ensembles perform better in summer and autumn in most European regions but tend to overestimate precipitation in winter and spring. PRIMAVERA shows improvements in the latter by reducing moderate-precipitation rate biases over central and western Europe. The spatial distribution of mean precipitation is also improved in PRIMAVERA. Finally, heavy precipitation simulated by PRIMAVERA agrees better with observations in most regions and seasons, while CORDEX overestimates precipitation extremes. However, uncertainty exists in the observations due to a potential undercatch error, especially during heavy-precipitation events.
The analyses also confirm previous findings that, although the spatial representation of precipitation is improved, the effect of increasing resolution from 50 to 12 km horizontal grid spacing in EURO-CORDEX daily precipitation distributions is, in comparison, small in most regions and seasons outside mountainous regions and coastal regions. Our results show that both high-resolution GCMs and CORDEX RCMs provide adequate information to end users at a 50 km scale.
How to cite: Demory, M.-E. and Berthou, S. and the PRIMAVERA and EURO-CORDEX co-authors: European daily precipitation according to EURO-CORDEX regional climate models (RCMs) and high-resolution global climate models (GCMs) from the High-Resolution Model Intercomparison Project (HighResMIP), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14363, https://doi.org/10.5194/egusphere-egu21-14363, 2021.
Land-use and land cover (LULC) are continuously changing due to environmental changes and anthropogenic activities. Many observational and modeling studies show that LULC changes are important drivers altering land surface feedbacks and land-atmosphere exchange processes that have substantial impact on climate on the regional and local scale. Yet, most long-term regional climate modeling studies do not account for these changes. Therefore, within the WCRP CORDEX Flagship Pilot Study LUCAS (Land Use Change Across Scales) a new workflow was developed to generate high-resolution annual land cover change time series based on past reconstructions and future projections. First, the high-resolution global land cover dataset ESA-CCI LC (~300 m resolution) is aggregated and converted to a 0.1° resolution, fractional plant functional type (PFT) dataset. Second, the land use change information from the land-use harmonized dataset (LUH2), provided at 0.25° resolution as input for CMIP6 experiments, is translated into PFT changes employing a newly developed land use translator (LUT). The new LUT was first applied to the EURO-CORDEX domain. The resulting LULC maps for past and future - the LUCAS LUC dataset - can be applied as land use forcing to the next generation RCM simulations for downscaling CMIP6 by the EURO-CORDEX community and in the framework of FPS LUCAS. The dataset includes land cover and land management practices changes important for the regional and local scale such as urbanization and irrigation. The LUCAS LUC workflow is applied to further CORDEX domains, such as Australasia and North America. The resulting past and future land cover changes will be presented, and challenges regarding the application of the new workflow to different regions will be addressed. In addition, issues related to the implementation of the dataset into different RCMs will be discussed.
How to cite: Hoffmann, P., Rechid, D., Reinhart, V., Asmus, C., Davin, E. L., Katragkou, E., de Noblet-Ducoudré, N., Böhner, J., and Bechtel, B.: Generating long-term high-resolution land-use change datasets for regional climate modeling in CORDEX domains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14967, https://doi.org/10.5194/egusphere-egu21-14967, 2021.
The Weather Research and Forecasting (WRF) model version 4.2 includes different land surface schemes, allowing a better representation of the land surface processes. Four simulations with the WRF model differing in land surface models and options were investigated as a sensitivity study over the European domain. These experiments span from 2004-2006 with a one-month spin-up and were performed at 0.11o horizontal resolution with 50 vertical levels, following the CORDEX guidelines. The lateral boundary conditions were driven by ERA5 reanalysis from European Centre for Medium-Range Weather Forecasts. For the first experiment, the Noah land surface model was used. For the remaining simulations, the Noah-MP (multi-physics) land surface model was used with different runoff and groundwater options: (1) original surface and subsurface runoff (free drainage), (2) TOPMODEL with groundwater and (3) Miguez-Macho & Fan groundwater scheme. The physical parameterizations options are the same for all simulations. These experiments allow the analysis of the sensitivity of different land surface options and to understand how the representation of land surface processes impacts on the atmosphere properties. This study focusses on the investigation of land-atmosphere feedbacks trough the analysis of the soil moisture – temperature and soil moisture – precipitation interactions, latent and sensible heat fluxes, and moisture fluxes. The influence of different surface model options on atmospheric boundary layer is also explored.
Acknowledgements. The authors wish to acknowledge the LEADING (PTDC/CTA-MET/28914/2017) project funded by FCT. The authors would like to acknowledge the financial support FCT through project UIDB/50019/2020 – Instituto Dom Luiz.
How to cite: Lima, D. C. A., Cardoso, R. M., and Soares, P. M. M.: Response of the surface climate to different land surface models: WRF sensitivity to surface model options, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15663, https://doi.org/10.5194/egusphere-egu21-15663, 2021.
The correct representation of air-sea coupling is crucial towards improving the Indian summer monsoon. In this study, a coupled atmosphere-ocean regional model ROM is employed to investigate the impact of horizontal resolution (0.440 and 0.220) in simulating the mean Indian summer monsoon characteristics and associated dynamical and thermodynamical processes. Regional model, REMO, and global ocean model, MPIOM is taken as atmospheric and ocean components of the coupled system. Interestingly, ROM at both resolutions performs well in simulating the mean monsoonal characteristics. However, increasing horizontal resolution from 0.440 to 0.220 adds value in simulating the JJAS mean precipitation by reducing the biases both over ocean and land. The detailed results from the analysis will be discussed in the general assembly.
Keywords: Indian summer monsoon, coupled regional model, horizontal-resolution, CORDEX-SA
Acknowledgement: This work is jointly supported by the Department of Science and Technology (DST), Govt. of India, grant number DST/INT/RUS/RSF/P-33/G and the Russian Science Foundation (Project No.: 19-47-02015).
How to cite: Kumar, P., Mishra, A. K., Dubey, A. K., Saharwardi, Md. S., and Sein, D.: Impact of Horizontal Resolution on Indian Summer Monsoon in coupled Atmosphere-Ocean Regional Model over CORDEX-SA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15990, https://doi.org/10.5194/egusphere-egu21-15990, 2021.
As a result of global warming, the magnitude and the frequency of extreme hot temperature events have increased remarkably in the recent decades. In the absence of policies, global warming is expected to continue during the next years, and certain regions which are already characterized by warm and hot temperatures, such as the Euro-Mediterranean region, may be notably impacted in numerous and diverse fields. The aeronautical sector is among these vulnerable fields, as aircraft takeoff performances also depend on air temperature. For instance, an increase in ground temperature results in a decrease in air density, and consequently in the available thrust for takeoff. This may lead to flight delays, weight restrictions or even flight cancellations. Concerning the aircraft engines, an increase in temperature may negatively impact the performance and may also lead to an increase of pollutant emissions into the atmosphere. All of these effects would have a social, economic and health impact.
In this study we analyze the evolution of extreme hot temperatures on aircraft performance over the main airports in the Southern Euro-Mediterranean region, using simulations performed by regional climate models (RCMs) from the Euro-CORDEX international exercise. To this end, we first evaluate RCMs in terms of their representation of extreme hot temperatures and their trends in the present period by comparing to different observational datasets and also to the driving GCMs. The results of this comparison show that RCMs don't represent better the amplitude nor the temporal trends of hot temperature events in summer, despide their higher spatial resolution. We assess the changes in the hot temperature extremes from the Euro-CORDEX future projections and we evaluate the risk of weight restriction in the next decades.
How to cite: Gallardo, V., Sanchez-Gomez, E., and Riber, E.: Evolution of extreme hot temperatures over Euro-Mediterranean main airports , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16115, https://doi.org/10.5194/egusphere-egu21-16115, 2021.
Forecasted trends of solar radiation and wind speed serve as an input for climate risk assessment as well as the estimation of renewable energy potential in the future climate.
In the frame of the project “Adaption strategies to Climate Change in Poland” the projections of solar radiation and the wind speed were developed based on the EURO-CORDEX. The RCM results for an area covering central Europe with a resolution of 0.11 ° (approx. 12.5 km) were used. The analyses were carried out for RCP4.5 and RCP8.5 scenarios.
To represent better the local variability the statistical downscaling was applied based on various historical gridded datasets (ERA5 and IMWM for the wind speed and ERA5, IMWM, and SARAH-II for the shortwave solar radiation). Ensemble analyses were undertaken to assess the projection uncertainty.
Solar radiation in the future climate shows a slight downward trend. The annual sum of solar radiation at the end of the century will decrease by 12 kWh/m2 to 40 kWh/m2, depending on the scenario. The most significant change will occur in eastern and north-eastern Poland. Forecasts of average wind speed values do not indicate significant changes in the 21st century, although the wind speed distribution showed changes in individual months - an increase in the winter and a decrease in the summer months.
Results are available via the interactive climate web portal https://klimada2.ios.gov.pl/klimat-scenariusze-portal/.
How to cite: Struzewska, J., Jefimow, M., Gienibor, A., Kleczek, M., Sattari, A., Zdunek, M., Norowski, A., and Walczak, B.: Radiation and wind projections for Poland based on downscaled EuroCORDEX ensemble, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16153, https://doi.org/10.5194/egusphere-egu21-16153, 2021.
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