CL2.4

Despite continued progress and a growing literature assessing regional climate change worldwide, modeling and assessing climate characteristics in mountainous regions remain challenging. Yet the stakes are high in these regions. As significant changes affect glaciers and snowpack, having
cascading effects on regional hydrology, quantifying them as accurately as possible is necessary for societal actors to adapt and reduce the growing climate risks.

Convection permitting climate modelling is a promising avenue for climate change research and services, particularly in mountainous regions. Work is required to evaluate the results of high resolution simulations against relevant reference dataset and put them in a broader context against coarser resolution modeling frameworks.

Our research assesses the potentials and limitations of high resolution climate models to represent past and future changes in snow conditions in the European Alps.

Here, we present an insight from the convection permitting climate model (CPRCM) CNRM-AROME ran at 2.5 km horizontal resolution over a large pan-Alpine domain in the European Alps, using either the ERA-Interim or CNRM-CM5 output as boundary conditions.

Annual and seasonal characteristics of four variables (2m temperature, total precipitation, solid fraction of precipitation and snow depths) are compared over the French Alps with the local reanalysis S2M, and raw or adjusted, with the ADAMONT method, simulations of the regional
climate model CNRM-ALADIN driven either by the ERA-Interim reanalysis or the CNRM-CM5 global climate model.

The study generally highlights similar differences in past and future climate between the datasets, as well as obstacles to the use of some CNRM-AROME outputs as they stand. These consist of excessive accumulation of snow on the ground above 1800 m a.s.l., as well as lower temperature
values at same elevations than the S2M reanalysis and the ADAMONT-adjusted outputs.

Nevertheless, clear advantages of CNRM-AROME simulations compared to raw CNRM-ALADIN outputs appear, concerning the temperature fields, the better representation of precipitations, as well as the spatial variability closer to the reference data.

How to cite: Monteiro, D., Caillaud, C., Samacoĩts, R., Lafaysse, M., and Morin, S.: Potential and limitations of convection-permitting CNRM-AROME climate modelling in the French Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4886, https://doi.org/10.5194/egusphere-egu22-4886, 2022.

In the last decade, records have been broken in Turkey's temperature and precipitation observations. In 2020, including the effect of increasing urbanization, the measured temperatures in Istanbul were about 3 °C higher than the 100-year monthly average. In addition, the frequency and intensity of excessive precipitation, especially in northern Turkey, show an increasing trend. Moreover, the change in precipitation patterns is also observed due to climate change. Therefore, to decide Turkey's strategies to combat climate change, it is necessary to determine how accurately the climate model results reflect these changes. For this reason, this study aims to determine the biases of the historical climate models compared with observations. Moreover, comparisons of these models with mild and dramatic scenarios in the CMIP5 and CMIP6 protocols are discussed. The climate models (INM-CM4 and INM-CM5; CNRM-CM5.2 and CNRM-CM6-1; and MRI-ESM1 and MRI-ESM2-0) that were not analyzed before were studied to construct an ensemble overall. Thus, it is aimed to create climate model ensembles for temperature and precipitation. Accuracies of the selected climate models are analyzed by comparing the results of the models with the observations in the 1965-2015 periods utilizing ten-year probability distribution fractions. In addition, simple Daily precipitation intensity index (ECASDII), precipitation days index (ECAPD), extremely wet days index (ECAR99P) analyzes for precipitation and very warm days index (ECATX90P), warm nights index (ECATN90P), and intra-temperature analysis for precipitation. -period extreme temperature range (ECAETR) indices were analyzed. Preliminary results show that climate models simulate temperature changes more accurately than precipitation changes for Turkey. In addition, CMIP6 results were more advantageous than CMIP5 results.

How to cite: Hazar, I., Aksu, A. N., Yogun, B., Dursun, B. C., and Tan, E.: Analysis of Historical Climate Scenarios of Turkey related to temperature and precipitation for comparing CMIP5 and CMIP6 protocols., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12357, https://doi.org/10.5194/egusphere-egu22-12357, 2022.

Located in the semi-arid region, Turkey is much more vulnerable to the drought effects of climate change. It is expected that the severity, duration, and frequency of drought episodes will increase due to climate change. The observations reveal that the drought episodes in Turkey have increased dramatically over the last decade. For example, in 2020, the occupancy rates of dams in Istanbul dropped below 30%. Therefore, the accuracy of the projections of climate models is essential in developing adaptation strategies related to drought types. Therefore, the study aims to compare the bias of the runoff and moisture content of the climate projection models (NorESM1-M and NorESM2; FGOALS-g2 and FGOALS-g3; and GFDL-CM3 and GFDL-CM4) with the observations. In addition, the scenarios in the CMIP5 and CMIP6 protocols were compared by calculating the probability distribution functions of the flow data for ten-year periods. In addition, consecutive dry days index (ECACDD), warm spell duration index (ECAHWFI), water storage deficit index, and Palmer drought severity index are also analyzed. Preliminary conclusions indicate that climate models vary significantly in capturing historical events. For this reason, an ensemble of the models needs to be created for decision-making purposes.

How to cite: Dursun, B. C., Yogun, B., Hazar, İ., Aksu, A. N., and Tan, E.: Comparisons of historical CMIP5 and CMIP6 protocols for the drought indices of Turkey, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12365, https://doi.org/10.5194/egusphere-egu22-12365, 2022.

The spatio-temporal heterogeneity in surface characteristics is considered to play a key role in terrestrial surface processes. Its characterization is essential for adaptation strategies. Here, we conducted regional climate simulations with COSMO-CLM (v5.0_clm16) with different land cover input data driven by ERA5 reanalysis over Germany at convection-permitting horizontal resolution of 3 km from 2000 to 2011. The difference between the land cover data of GLC2000, CCI_LC and ECOCLIMAP and the operational used GLOBCOVER2009 dataset on temperature and its extremes is investigated. The results reveal that the differences in turbulent fluxes and temperature are related to land cover classes. Even though the land cover class fractional differences are small among the land cover maps, some land cover types, such as croplands and urban areas, have greatly changed over the years. These distribution changes can be seen in the temperature differences. Simulations based on the CCI_LC retrieved in 2000 and 2015 revealed no accreditable difference in the climate variables as the land cover changes that occurred between these years are marginal, and thus, the influence is small over Germany. Increasing the land cover types as in ECOCLIMAP leads to higher temperature variability. The largest differences among the simulations occur in maximum temperature and from spring to autumn, which is the main vegetation period. The temperature differences seen among the simulations relate to changes in the leaf area index, plant coverage, roughness length, latent and sensible heat fluxes due to differences in land cover types. The vegetation fraction was the main parameter affecting the seasonal evolution of the latent heat fluxes based on linear regression analysis, followed by roughness length and leaf area index. If the same natural vegetation (e.g. forest) or pasture grid cells changed into urban types in another land cover map, daily maximum temperatures increased accordingly. Similarly, differences in climate extreme indices (e.g., SU or TR) are strongest for any land cover type change to urban areas. The uncertainties in regional temperature due to different land cover datasets were overall lower than the uncertainties associated with climate projections. Although the impact and their implications are different on different spatial and temporal scales as shown for urban area differences in the land cover maps. Thus, to realistically simulate land use/cover change effects on regional and local climate and draw conclusions for management strategies, numerical models would benefit from land surface characteristics, which are as accurate as possible in retrieval year, number of land cover classes, their distribution and fractions and have a high spatial resolution.

How to cite: Tölle, M. and Churiulin, E.: The role of different land cover input data on local climate and its extremes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6507, https://doi.org/10.5194/egusphere-egu22-6507, 2022.

Urbanization alters land surface properties and the local surface energy balance and, therefore, land and near surface air temperature. Urban morphology and processes are represented in climate models using urban land-surface models with varying levels of complexity, which parameterise the effects of urban environments on surface fluxes without representing buildings explicitly.

This study focuses on the eastern Mediterranean and the Middle East (EMME) area over which the effect of urban parameterisation and resolution difference on simulated 2-meter air and land surface temperatures is investigated. Two high-resolution simulations at 16 km and 4 km are performed over the EMME domain using the Weather Research and Forecasting (WRF) model coupled with NoahMP land surface scheme for the period of 2000-2002. The bulk urban parameterisation scheme is implemented, which assigns fixed values for land properties such as surface albedo, roughness length etc., appropriate for the resolved urban areas. Focusing on several cities of the region of interest for the summer season (June-July-August, JJA), the effect of the model horizontal resolution and the grid-box land type on air (minimum and maximum) and land temperatures is examined. The temperature difference of the urban-characterised grid-boxes compared to their rural surroundings is also studied. Station (Integrated Surface Dataset - ISD) and satellite (MODIS-TERRA) observations together with reanalysis data (ERA5-LAND) are used for the evaluation of the simulation output.

How to cite: Constantinidou, K., Hadjinicolaou, P., Tzyrkalli, A., Zittis, G., and Lelieveld, J.: How are air and land temperatures affected by the horizontal resolution and the bulk urban parametrisation in WRF model simulations over the eastern Mediterranean and the Middle East?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4610, https://doi.org/10.5194/egusphere-egu22-4610, 2022.

Detailed information about extreme precipitation is crucial due to the impacts on the human environment. Recently, high-resolution regional climate models (RCMs) are run at convection-permitting scales to investigate the regional precipitation extremes. The Black Sea region is one of the intriguing regions for modelling studies because of its distinctive topographical features where orographic forcing and strong air-sea interactions intensify destructive heavy precipitation. Recently, RCMs have been tested in order to find the most suitable configuration to represent precipitation over this region. Although the historical simulations are beneficial to test the model performance, model configurations may exhibit different spatiotemporal characteristics in simulating extreme precipitation due to the shift of the seasons in a possible warmer future. Recent studies focusing on the intensification of extreme precipitation events highlighted the model sensitivity to increasing sea surface temperature (SST) over the Black Sea. Therefore, future simulations focusing on different model configurations may provide valuable information to understand the response of RCMs in a changing climate. In this study, we downscaled the last generation CMIP6 MPI-ESM1.2-HR outputs by using the WRF model at 3 km horizontal resolution to test the model’s sensitivity for different microphysical and planetary boundary layer (PBL) parameterization options under the SSP5-8.5 future socioeconomic global change scenario. We selected cold and warm extreme precipitation cases and performed 3-days convection-permitting simulations over the complex topography of the Black Sea region. For the cold case, simple single-moment schemes produced less precipitation compared to more complex schemes, especially over the mountains, because of the insufficient representation of snowfall. For the warm case, the difference between the simulations is similar to the cold case but, the magnitude is lower. The change of the PBL scheme affects the vertical and horizontal distribution of microphysical properties and precipitation distribution near the coasts and the mountains.

How to cite: Kelebek, M. B. and Önol, B.: Sensitivity to Microphysics and PBL Schemes for Extreme Precipitation over the Black Sea Region in Future Climate: Warm and Cold Cases, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-408, https://doi.org/10.5194/egusphere-egu22-408, 2022.

Regional winds are usually caused by small pressure differences, and so air flows arise in very specific areas. When these air flows pass through certain orographic features over the Iberian Peninsula, such as channels like the Ebro Valley or the Strait of Gibraltar, they acquire a certain range of directions and considerable speed due to mass conservation. However, reanalysis products are not able to analyze them because their spatial resolution, larger than 10 km, is usually not high enough to properly describe the orographic characteristics that lead to these regional winds. Here, we explore the application of the COSMO-REA6 very high resolution reanalysis system to study three regional winds in the Iberian Peninsula: Cierzo in the Ebro Valley and Levante and Poniente in the Strait of Gibraltar, for the 2000-2018 period. COSMO-REA6 has a spatial resolution of 6 km (0.055º), much larger than the other current state-of-the-art reanalysis, and so it could better capture regional winds due to its better orographic representation. Cierzo, Levante and Poniente are very relevant due to their intensity and frequency over the regions. Defined with a 5 m/s threshold for each hour and their specific direction range, around 95, 85 and 82 wind days per year are obtained, respectively. Comparison against the small amount of observational data shows that there is reasonable conformity between datasets in terms of statistics and annual cycles. Reanalysis allows us to study regional wind spatial features such as extension statistics (frequency, covered area) of Cierzo along the Ebro Valley or Levante/Poniente over the Strait of Gibraltar. Atmospheric patterns associated with these regional winds indicate great differences between winter and summer patterns. This study aims to increase the current small number of studies focused on regional winds over Europe, with clear interests on wind climatology, meteorological characterization of atmospheric flows and other applications such as renewable energy production.

How to cite: Ortega, M., Sánchez, E., Gutiérrez, C., and Molina, M. O.: Regional winds over the Iberian Peninsula (Cierzo, Levante and Poniente) from high resolution COSMO-REA6 reanalysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2201, https://doi.org/10.5194/egusphere-egu22-2201, 2022.

Precipitation is changing as the climate warms. Downpours can potentially become more intense, frequent, and of longer duration due to the increased water holding capacity of the atmosphere and other (thermo)dynamical responses. However, the exact nature of the precipitation response and its characteristics are still not well understood due to the complex nature of the physical processes underlying the formation of clouds and precipitation. 

In this study, present and future Norwegian climate are simulated at convection-permitting scales with a regional climate model. Hourly precipitation is separated into three categories (convective, stratiform, and orographically enhanced stratiform). This is achieved using a physically-based algorithm that is tested over different mountainous areas. 

We investigate changes in the frequency, intensity and duration of precipitation events for each category, delivering a more nuanced insight into the precipitation response to a changing climate. Results show a significant intensification of autumn precipitation and more frequent convective precipitation. The precipitation response in autumn and spring deviates from the idealised thermodynamic response, partly owing to changes in cloud microphysics. These results show that changes in the precipitation distribution are affected in complex ways by the local climatology, terrain, seasonality and cloud processes. Given the societal impacts of intense rainfall, there is an imperative to further understand these complexities, thus enabling greater societal resilience to climate change.

How to cite: Poujol, B., Sobolowski, S., and Mooney, P.: Physical processes driving intensification of future precipitation in the mid- to high latitudes: an example from Norway, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-125, https://doi.org/10.5194/egusphere-egu22-125, 2022.

Mesoscale Convective Systems (MCS) are common over Europe during the warm season (Morel and Senesi, 2002b) and are able to produce severe weather such as extreme precipitation leading to flash floods (Fiori et al., 2014). Studies analyzing the climatological characteristics of MCS over Europe are rare and were often based on only a few years of data or were focused on a limited area of Europe. In their recent research, Surowiecky and Taszarek (2020) showed that MCS over Poland can frequently adopt typical morphology of mid-latitude extreme-rain producing MCS (Schumacher and Johnson, 2005).
With the recent Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG; Huffman et al., 2019) satellite precipitation climatology, we identify and track MCS for nearly 20 years over Europe. Our detection/tracking algorithm is inspired from the one proposed by Feng et al. (2021). Cell-tracking from precipitation data is not straightforward, especially for fast moving and small systems. Here, we make use of a spatio-temporal filter and track cells according to the overlapping of filtered precipitation patches between two consecutive time steps. We fit an ellipse to the precipitating patches for a quick scan of their morphology and orientation. The algorithm is able to distinguish between non-convective rain bands from convective rain patches, thus reducing potential identification errors.
We use this new European MCS climatology to evaluate their main characteristics in Europe and their potential evolution over the last 20 years. In particular, we examine their occurrence frequency in extreme rainfall events in this region and the environmental conditions leading to these extremes, with respect to other (non-MCS) convective systems. This work contributes to better understanding the role that convective organization plays in driving extreme rain in mid-latitudes from an observational perspective.

References

Feng Z, Leung LR, Liu N, Wang J, Houze RA, Li J, Hardin JC, Chen D, Guo J. 2021. A global high-resolution mesoscale convective system database using satellite-derived cloud tops, surface precipitation, and tracking. Geophys. Res. Atmos., 126, e2020JD034202, doi: 10.1029/2020JD034202. 

Fiori E, Comellas A, Molini L, Rebora N, Siccardi F, Gochis D, Tanelli S, Parodi A. 2014. Analysis and hindcast simulations of an extreme rainfall event in the Mediterranean area: the Genoa 2011 case. Atmos. Res., 138, pp. 13–29, doi: 10.1016/j.atmosres.2013.10.007.

Huffman GJ, Stocker EF, Bolvin DT, Nelkin EJ, Tan J. 2019. GPM IMERG final precipitation L3 half hourly 0.1 degree x 0.1 degree V06, Greenbelt, MD, Goddard Earth Sciences Data and Information Services Center. doi: 10.5067/GPM/IMERG/3B-HH/06.

Morel C, Senesi S. 2002b. A climatology of mesoscale convective systems over Europe using satellite infrared imagery. II: Characteristics of European mesoscale convective systems. Quart. J. Roy. Meteor. Soc., 128, 1973–1995, doi: 10.1256/003590002320603494.

Schumacher RS, Johnson RH. 2005. Organization and environmental properties of extreme-rain-producing mesoscale convective systems. Month. Weath. Rev., 133, 961–976, doi: 10.1175/MWR2899.1.

Surowiecki, A., & Taszarek, M. (2020). A 10-Year Radar-Based Climatology of Mesoscale Convective System Archetypes and Derechos in Poland, Month. Weath. Rev., 148(8), 3471–3488, doi: 10.1175/MWR-D-19-0412.1.

How to cite: Da Silva, N. and Haerter, J.: The role of mesoscale convective organization in the generation of extreme precipitation over Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5483, https://doi.org/10.5194/egusphere-egu22-5483, 2022.

Extreme precipitation and temperature events (EPTE) cause devastating impacts to ecosystems and society. The diversity of climates around the world does not allow a single definition of extreme events given the multiplicity of conditions in which each event develops. In regions of complex topography, interactions with vegetation have as a result numerous atmospheric circulation patterns and the existence of various phenomena at different spatial and temporal scales, which impedes homogeneity of distribution, frequency, and intensity of extreme events. It is known that El Niño Southern Oscillation (ENSO) influences the interannual variability of precipitation and temperature in different regions around the world. However, it is not clear how this phenomenon interacts with the frequency and intensity of EPTE in regions with complex topography gradient and a diversity of climates. Here we focus on the Colombian Andes mountain range in northern South America because it occupies a quarter of the territory, gathers most of the socio-economic development, and concentrates the majority of the country´s population. In this context, we use statistical analysis to characterize EPTE during La Niña, El Niño, and neutral years. In this work, we also compare the frequency and intensity of EPTE between La Niña and neutral years and El Niño and neutral years. Unlike other studies, we want to know if there is any pattern of increase or decrease of EPTE when an ENSO phase is active. We discuss the months in which there is an increase or decrease in EPTE according to the interannual variability of precipitation and temperature, as well as the months in which there is a significant relationship between the sea surface temperature of the Niño 3.4 region with precipitation and temperature. Our results show that the highest intensities of extreme precipitation events occur in the rainy seasons March-April-May and September-October-November. Also, the highest frequency of extreme precipitation events occurs between December and March for both the 95th and 99th percentile. The difference analysis showed that during El Niño and La Niña periods, extreme precipitation events are more intense than in neutral years. Additionally, the frequency of events is higher during El Niño, but their localization is variable in time and space. The behavior of temperature extremes is more marked since the most intense events occur during El Niño from February to September, and the highest frequency of extreme events occurs between April and September and varies throughout the year in the Andes region according to the active phase of ENSO. These results provide a basis for the design of adaptation and mitigation policies in the face natural variability and climate change, and for improving hydrometeorological forecasts.

How to cite: Acero, I. C. and Vieira, S. C.: Characterization of extreme precipitation and temperature events during El Niño Southern Oscillation in the Colombian Andes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9008, https://doi.org/10.5194/egusphere-egu22-9008, 2022.

India experienced more flood situations due to the increasing extreme rainfall events over the different Indian River Basins (IRBs) during the last few decades. An Extreme Value Theory (EVT) is used to examine trends of rainfall extremes over the IRBs using long-term observed high-resolution grid-based rainfall (1901-2019) of the India Meteorological Department. The analysis depicts that when generalized extreme value theory (GEV) is applied to annual maximum rainfall over IRBs, statistically significant uniform trends were not seen. The spatial variations in the annual maximum rainfall for the 10-, 30- and 100-year return levels show statistically significant increasing trends over the IRBs. The shifting trend of rainfall extremes from northeast towards the western river basins of IRBs in the last two decades and resulted in damage to life and property on the west coast. The decadal changes in average intensity of dry and wet condition at 12- months running time window reveals that the shifting and increasing pattern of the rainfall extremes events during the last decades of the 20th century (1981-2000) and current decades of the 21st century (2001-2019) over the western ghats and west-flowing river basin leads to several floods situations. This research highlights the significant increasing trend in extreme rainfall events over the IRBs, which may pose a grave risk to agriculture, human life, and predominantly on the vulnerable sections of the society.

How to cite: Chaubey, P. K. and Mall, R. K.: Western shifting of Extreme Rainfall Events over the different Indian River Basins in the last 119 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-188, https://doi.org/10.5194/egusphere-egu22-188, 2022.

Hail is a significant convective weather hazard, often causing considerable crop and property damage across the world. Although extremely damaging, hail still remains a challenging phenomenon to model and forecast given the gaps in understanding the processes involved in hail formation. Recently, a physically-based one-dimensional hail model called HAILCAST was developed. HAILCAST forecasts the maximum expected hail diameter at the ground using a vertical profile of the updraft, temperature, liquid and ice water content and can be embedded within a convection-permitting model (CPM). Furthermore, lightning activity is a characteristic phenomenon that often accompanies severe weather, and especially hailstorms, as well as a damaging phenomenon in itself. One of the ways to diagnose the areas prone to lighting activity is by using a Lightning Potential Index (LPI). LPI is a measure of the potential for charge generation and separation inside a thundercloud, which results in lightning flashes during convective thunderstorms. Therefore, LPI maps the area with the potential for electrical activity based on the model’s dynamical and microphysical fields.

Here, eight hailstorms occurring over the Alpine-Adriatic region are analyzed using Weather Research and Forecasting (WRF) and Consortium for Small Scale Modeling in Climate Mode (COSMO) simulations with embedded HAILCAST and LPI at convection-permitting resolution (~2.2 km). In addition, a model intercomparison study is performed to investigate the ability of different modelling systems in reproducing such convective extremes and to further assess the uncertainties associated with simulations of such local-area phenomena. The results are verified by direct hail observations from Croatia (hailpad network), radar estimates of hail from Switzerland (probability of hail, maximum expected severe hail size) and lightning measurements from the LINET network.

The analysis revealed that both HAILCAST and LPI are able to reproduce the observed hail and lightning activity. Namely, both models are able to capture the areas affected by hail and lightning as well as its intensity. Moreover, the fields produced by both models are remarkably similar, although, a slight tendency of WRF to produce smaller hail swaths with larger hailstone diameters and larger LPI values seems to be present. Overall, the analysis revealed promising results and indicates that both HAILCAST and LPI could be valuable tools for real-time forecasting and climatological assessment of hail and lightning occurrence in current and possibly changing climate.

How to cite: Malečić, B., Cui, R., Jelić, D., Horvath, K., Telišman Prtenjak, M., Ban, N., Demory, M.-E., Mikuš Jurković, P., Strelec Mahović, N., and Schär, C.: Performance of HAILCAST and lightning potential index coupled with WRF and COSMO in convection-permitting simulations of hailstorms over the Alpine-Adriatic region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2499, https://doi.org/10.5194/egusphere-egu22-2499, 2022.

Due to associated hydrological risks, there is an urgent need to provide plausible quantified changes in future extreme rainfall rates. Convection-permitting (CP) climate simulations represent a major advance in capturing extreme rainfall and its sensitivities to atmospheric changes under global warming. However, they are computationally costly, limiting uncertainty evaluation in ensembles and covered time periods. This is in contrast to the Climate Model Intercomparison Project (CMIP) 5 and 6 ensembles, which cannot capture relevant convective processes, but provide a range of plausible projections for atmospheric drivers of rainfall change. Here, we quantify the sensitivity of extreme rainfall within West African storms to changes in atmospheric rainfall drivers, using both observations and a CP projection representing a decade under the Representative Concentration Pathway 8.5 around 2100. We illustrate how these physical relationships can then be used to reconstruct better-informed extreme rainfall changes from CMIP, including for time periods not covered by the CP model. We find reconstructed hourly extreme rainfall over the Sahel increases across all CMIP models, with a plausible range of 37-75% for 2070-2100 (mean 55%, and 18-30% for 2030-2060). This is considerably higher than the +0-60% (mean +30%) we obtain from a traditional extreme rainfall metric based on raw daily CMIP rainfall, suggesting such analyses can underestimate extreme rainfall intensification. We conclude that process-based rainfall scaling is a useful approach for creating time-evolving rainfall projections in line with CP model behaviour, reconstructing important information for medium-term decision making. This approach also better enables the communication of uncertainties in extreme rainfall projections that reflect our current state of knowledge on its response to global warming, away from the limitations of coarse-scale climate models alone.

How to cite: Klein, C., Parker, D. J., Jackson, L. S., Marsham, J. H., Taylor, C. M., Rowell, D. P., Guichard, F., Vischel, T., Famien, A. M., and Diedhiou, A.: Combining CMIP data with a convection-permitting model and observations to project extreme rainfall under climate change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5269, https://doi.org/10.5194/egusphere-egu22-5269, 2022.

In the warming climatic scenario, Indian Summer Monsoon (ISM) rainfall and its extremes, especially on the local scale, is expected to alter that profoundly impact the societal, environmental, and economic well-being of the million people residing in central India. Therefore, understanding ISM mean and extreme rainfall for the past, current, and reliable projection are crucial for effective adaptation strategies, remains a major scientific challenge. The Regional Earth System Model (ROM) driven by MPI-ESM-LR over the CORDEX-South Asia framework under the RCP8.5 scenario at a finer horizontal resolution of 0.22° was used to investigate the future of mean and extreme precipitation over central India. The ROM’s performance is demonstrated with respect to observed precipitation data from India Meteorological Department. ROM shows its skill in capturing the mean and extreme precipitation (PEs) during the ISM along with its intraseasonal variability.  Further, an effort is made to investigate the projected changes in precipitation extremes (PEs) during the mid-future (MF; 2040-2069) and far-future (FF; 2070-2099) concerning the historical period (1969-2000) under the RCP8.5 scenario. The results highlight, two-fold rise in the frequency of PEs is likely to be expected by the end of the century. In addition to this, the study also projects the intraseasonal variability, i.e., the active and break spells that crop up during the peak monsoon months (July and August). The active spells were found to be more persistent in the projected period. The changes in the different precipitation events are subjected to strong cyclonic circulation, reduced vertical wind shear, and enhanced moisture transport.

How to cite: Kumari, A. and Kumar, P.: Precipitation Extremes over central India - Past, Present, and Future: Regional Earth System Model Perspective, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-289, https://doi.org/10.5194/egusphere-egu22-289, 2022.

Profound changes have been observed in the precipitation pattern of Turkey due to climate change during the last decade. This variation in precipitation pattern affects the amount of snow cover and the temporal and spatial distribution of snow. In addition, significant variability was observed in the initial time of snowmelt that water resources, especially groundwater, might be adversely affected. On the other hand, this adverse effect in snow cover is also crucial for Turkey's winter sports tourism. For this reason, the study aims to analyze the historical simulation results of climate models (MIROC5 and MIROC6; CanESM2 and CanESM5; and GISS-E2-H and GISS-E2-1-H) based on CMIP5 and CMIP6 protocols depending on snow cover variables and compare the consistency of these models with observations. Probability distribution functions of surface snow area fraction and snowfall flux variables over ten-year periods were analyzed. In addition, the frost days index (ECAFD), Ice days index (ECAID), and very cold days (ECATX10P) index were also analyzed. As a preliminary result, it was found that the snow cover values of the CMIP6 protocol climate models were more consistent with the observations.

How to cite: Aksu, A. N., Hazar, I., Dursun, B. C., Yogun, B., and Tan, E.: Snow Cover Analysis of Turkey comparing to Historical Climate Scenarios of CMIP5 and CMIP6 protocols, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12312, https://doi.org/10.5194/egusphere-egu22-12312, 2022.

Flash floods rank among the most dangerous and costliest hazards of the alpine and mediterranean region. The severe convective storms causing them are influenced by both, the presence of a large body of sea water and a complex orography. These storms are the main subject of the present study and in the following referred to as heavy precipitation events (HPEs).

We here study heavy precipitation events by using an ensemble of convection permitting regional climate models and applying a tracking algorithm, and focus on their charateristic properties. The domain covers the Alps and the central part of the Mediterranean, and we investigate and compare three 10-year periods under the rcp85 forcing scenario: historical [2000-2009], near-future [2040-2049] and far-future [2090-2099].

Our analysis reproduces a most important message: even though in the future the mediterranean climate is drying, precipitation associated with heavy precipitation events is increasing. Further, HPEs will be more frequent in the future. In particular, their occurrence frequency will increases in wintertime, whereas it will decrease in summertime.

We investigate the climate change signal of characteristic properties describing the propagation, the spatial and temporal scales and the intensity of HPEs: on average HPEs travel by 10% farther [8km], they last longer by 5% [20 min], their area increases by 16% and their total rain volume by 34%. Regarding metrics of intensity the changes of the highest percentiles are greatest: the 90th percentiles of a HPE's precipitation field increases by 5.6%, the 99th percentile by 9.4% and the maximum increases by 12.7%.

Eventually we unravel the characterics for specific regions and seasons: changes are more dramatical for HPEs that cross the coastline and in wintertime.

In summary, this study confirms important messages of climate research in an ensemble of state-of-the-art regional climate models, demonstrates the capabilities of convection-permitting spatial resolution and explores the possibilities that come with applying a tracking algorithm and by looking into precipitation extremes in the Lagrangion framework of reference.

How to cite: Müller, S. K., Pichelli, E., Coppola, E., Berthou, S., Brienen, S., Caillaud, C., Demory, M.-E., Dobler, A., Feldmann, H., Mercogliano, P., Tölle, M., and de Vries, H.: A Climate Change Study of Heavy Precipitation Events in the Mediterranean and Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5481, https://doi.org/10.5194/egusphere-egu22-5481, 2022.

Subdaily extreme precipitation may trigger fast hydro-geomorphic responses, such as flash floods and debris flows, which cause numerous fatalities and large damage. Compared to coarser resolution models, high-resolution models, called convection-permitting (CPMs), more realistically represent convective processes that are key for the correct representation of subdaily extremes, and thus provide higher confidence in the future extreme estimates. However, due to the high computational demands, the existing CPM simulations are only available for relatively short time periods (10–20 years at most), too short for deriving precipitation frequency analyses with conventional approaches. Recent extreme value analysis methods, based on all “ordinary” observations rather than on just yearly maxima or a few values over a high threshold, offer an opportunity for exploiting these short data records to reliably estimate return levels associated with long return periods. Here, we examine subdaily precipitation extremes from three 10-year time slices (historical 1996-2005, near-future 2041-2050, and far future 2090-2099 – under the RCP8.5 scenario) of COSMO-crCLIM model simulations at 2.2 km resolution. We focus on the Eastern Alpine transect characterised by a complex orography, where significant changes in subdaily annual maxima have been already observed. We find that, although the storms' frequency will decrease in the region, the mean annual maxima will increase continuously in the near and far future, especially at shorter durations. Investigation of extreme return levels shows a similar trend, with larger changes in the far future. A shift in the seasonality is also reported, with extremes moving from late summer-autumn (historical), to autumn (near future), and autumn-winter (far future).

How to cite: Roghani, B., Dallan, E., Fosser, G., Schär, C., Marani, M., Borga, M., and Marra, F.: Changes in future subdaily extreme precipitation at convection-permitting scale over an alpine transect, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5924, https://doi.org/10.5194/egusphere-egu22-5924, 2022.

Recent research with “km-scale” or “convection-permitting” climate models (resolutions with grid-spacing generally < 4km) has described substantial improvements in the representation of precipitation when compared to conventional parameterized models. In particular, the distribution of precipitation is more faithfully reproduced and, in particular, precipitation extremes are more closely aligned with observations in terms of frequency, magnitude and duration. Future changes for many regions largely follow the mantra “the extremes become more extreme”. These results imply serious consequences arising from impacts commonly associated with extreme precipitation such as flash flooding, landslides, as well as  water resources availability. However, questions remain regarding the robustness of these responses as well as which types of precipitation contribute (and how) to the projected changes. Most of the existing literature at convection permitting scale consists of one or two model experiments and characteristics of precipitation are often defined based on arbitrary intensity thresholds. 

Here we employ the coordinated, multi-model ensemble of convection-permitting simulations generated within the WCRP CORDEX Flagship Pilot Study on Convection over Europe and the Mediterranean. While the domain covers the greater Alpine region we focus here on the Alps themselves given its exposure to a  wide variety of storm types and extremes and the importance of representing convection and its interactions with the complex topography for the local climate. This multi-model ensemble is now complete and the present paper investigates the changing characteristics of precipitation over the complex terrain of the Alps.

A physically-based algorithm is employed to categorize precipitation as either convective, stratiform or orographic. The algorithm was specifically designed for use with km-scale modeling and uses commonly available variables on only a few levels of the atmosphere. This algorithm has been shown previously to accurately categorize precipitation types over the Scandanavian mountains as well as the Alps. 

The results show strong decreases in annual convective and orographic precipitation over the greater Alpine region, while stratiform precipitation changes little if at all. Upon closer inspection, using the Analysis of precipitation across scales method (AsoP) and traditional IDF analyses, a more nuanced picture emerges. IDF plots show that the frequency of high intensity events increases, across all durations over all Alpine regions (NW, NE, S). Conversely, frequency decreases for more moderate events, most strongly in the summer season. The AsoP analysis shows that this occurs due to a shifting of the entire distribution of precipitation for all precipitation types. This shift to higher intensities comes at the expense of more moderate intensity events, which decrease. While all seasons show similar patterns of change the change is most pronounced in summer. Convective and orographic precipitation show similar patterns but the magnitude of the change is largest for convective precipitation. Thus, despite an overall drying over the Alps, the extremes indeed become more extreme and more frequent. This behavior is remarkably robust across the entire ensemble.

How to cite: Lorenz, T. and Sobolowski, S. and the CORDEX Flagship Pilot Study on Convection over Europe and the Mediterranean - ensemble on precipitation types: A robust shift towards higher intensity convective and orographic rainfall over the Alps in a warmer climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7066, https://doi.org/10.5194/egusphere-egu22-7066, 2022.