Session CL2.4

[Programme]

CL2.4 | Local scale climate change impacts, processes and extremes

Local scale climate change impacts, processes and extremes

Co-organized by AS1

Convener: Edmund Meredith | Co-conveners: Merja Tölle, Stefan Sobolowski, Giorgia Fosser, Erika Coppola

Orals

| Wed, 26 Apr, 14:00–15:15 (CEST)

Room 0.31/32

Posters on site

| Attendance Wed, 26 Apr, 16:15–18:00 (CEST)

Hall X5

Posters virtual

| Attendance Wed, 26 Apr, 16:15–18:00 (CEST)

vHall CL

This session explores climate change, extremes, processes and their impacts at local to regional scales, and the tools employed to investigate these phenomena. In particular, we welcome submissions advancing the state-of-the-art in the development and application of high-resolution models (convection-permitting, grid spacing ≤ 4 km) and high-resolution sub-daily data sets. Other high-resolution data sets such as land-surface, hydrology, vegetation or similar, and their impacts on local-scale climate change and extremes, are of further interest.

The session aims to bring together, amongst others, numerical modellers, the observational community and CORDEX-FPS participants, with the aim of advancing understanding of the aforementioned topics. Of particular interest are new insights which are revealed through high-spatiotemporal-resolution modelling or data sets. For example: convective extremes, physical mechanisms, fine-scale and feedback processes, differences in climate change signal, scale-dependency of extremes, interactions across scales and land-atmosphere interactions. Further, we welcome studies that explore local scale climate change in a variety of contexts whether they be past, present or future change. Studies that move towards an earth system approach – through incorporating coupled oceans, hydrology or vegetation – are especially encouraged.

Additional topics include, though are not limited to:
-- Mesoscale convective systems and medicanes
-- Event-based case studies (including surrogate climate change experiments or attribution)
-- Approaches for quantifying uncertainty at high resolutions including multi-model ensemble and combined dynamical-statistical approaches such as emulators
-- High-resolution winds and their impacts
-- Convection, energy balance and hydrological cycle including vegetation
-- Model setup and parametrization, including sensitivity to resolution, land surface and dynamics
-- Tropical convection and convective processes at local to regional scale
-- Model evaluation and new evaluation metrics/methods
-- Physical understanding of added value over coarser models
-- Severe storms including supercell thunderstorms and hailstorms
-- The roles of natural and internal variability

Note that the session will now be opened by the talk of Pichelli et al. and will be closed by the solicted talk of van Lipzig et al. Otherwise the order remains unchanged.

Additionally, the listed talk of Fildier et al. has been withdrawn and will be replaced by "Evaluation of precipitation variability over the Sierra de Guadarrama" by González-Rouco et al. (see session posters for abstract).

Orals: Wed, 26 Apr | Room 0.31/32

Chairperson: Giorgia Fosser

14:00–14:05

5-minute convener introduction

14:05–14:15

EGU23-11196

On-site presentation

Detection of disastrous convective events in the great alpine region and analysis of their sensitivity to the climate change

Emanuela Pichelli and the CORDEX-FPSCONV Team

An abnormal episode of high rain or snow is classified as heavy precipitation; its extreme intensity and driver mechanisms can vary a lot depending on location and season. The most extreme events can turn into a severe impact at ground (in terms of flood or flash-flood, human casualties and injuries, ecosystem and economy damages and losses).

We have implemented a method to detect the most extreme precipitation events trough 10-year long dataset of high-resolution observations and built on a list of the most disastrous ones occurred between 2000 and 2009 within the so called great alpine region (1°–17° East, 40°–50° North).

The method is then applied to the models belonging to the coordinated experiment CORDEX-FPS dedicated to convection and the ensemble at the convection permitting scale is able to represent the 70% of such kind of extreme events. The main drivers of the extreme precipitation are analysed and the factors affecting the model ability in correctly reproducing the unsuccessful cases are also investigated.

The same framework has been applied also to the model projections under the RCP8.5 scenario to study the sensitivity of such episodes and of their driving mechanisms to the climate change. The extreme events are projected to increase in frequency especially in the fall season over sub-regions with prevailing orographic forcing, whereas the events related to complex mesoscale interactions are projected to affect larger areas at the end of the century, posing the conditions of increased flood risk.

How to cite: Pichelli, E. and the CORDEX-FPSCONV Team: Detection of disastrous convective events in the great alpine region and analysis of their sensitivity to the climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11196, https://doi.org/10.5194/egusphere-egu23-11196, 2023.

14:15–14:25

EGU23-6829

ECS

On-site presentation

Land-atmosphere coupling in km-scale climate modeling: effects of resolution vs. land-surface model sophistication

Lorenzo Sangelantoni, Stefan Sobolowski, Rossella Ferretti, Gianluca Redaelli, Antonio Ricchi, and Enrico Scoccimarro

Recent studies exhibit a considerable reduction of summer season precipitation frequency in the new generation of convection-permitting (CP) climate simulations. This seems to over-correct non-CP wet biases with a knock-on effect on summer temperatures via soil moisture-atmosphere feedbacks. However, it is difficult to elucidate which part of the warmth/dryness in CP simulations can be ascribed to land-atmosphere coupling and/or "atmosphere-only" processes. Another layer of uncertainty belongs to the still crude representation of land surface/sub-surface processes that become especially relevant when approaching such high resolution.

In this study we explore the modulation of land-atmosphere coupling when moving from a non-CP to a CP-scale climate modeling, considering increasingly sophisticated land surface model configurations. We perform a two-step dynamical downscaling at ~15 km (convection-parameterized) and ~ 3km (convection-permitting) resolutions with the WRF-4.2.1 regional climate model driven by ECMWF-ERA5 reanalysis. The greater alpine region and the extended summer season (May to September) of 2003 are the spatial and temporal domains of interest. A mini multi-physics ensemble is generated with four Noah-MP land-surface model configurations to examine if, and how, including crucial land processes (e.g., vertical soil water transport) modifies hot-temperature forcing mechanisms in the two resolutions. Moreover, each ensemble member is run according to three different initial soil moisture levels, defining reference, anomalously dry- and wet-initialization experiments.

Preliminary results show an improved representation of precipitation statistics (seasonal cumulative, frequency, and 99^thpercentile) from CP simulations, particularly over complex orography. Generally, maximum temperature reproduction benefits from the CP scale. However, localized warm biases persist over flat terrains regardless of the land surface model configuration. Finally, the two resolutions show a substantially different decay of the initial soil moisture state. At CP scale all three runs converge to similar soil moisture at the end of the integration. Conversely, non-CP runs preserve large soil moisture differences until the end of the summer season, signaling longer soil moisture memory and different soil moisture-precipitation feedback.

These factors might significantly affect the reproduction and predictability of environmental and societal relevant hydroclimatic extremes on a wide-ranging temporal scale, from seasonal climate predictions to long-term climate projections.

How to cite: Sangelantoni, L., Sobolowski, S., Ferretti, R., Redaelli, G., Ricchi, A., and Scoccimarro, E.: Land-atmosphere coupling in km-scale climate modeling: effects of resolution vs. land-surface model sophistication, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6829, https://doi.org/10.5194/egusphere-egu23-6829, 2023.

14:25–14:35

EGU23-7501

Highlight

On-site presentation

The Dutch heat wave of July 2019 in a warmer world: How much hotter could it get?

Hylke de Vries, Geert Lenderink, Erik van Meijgaard, Wim de Rooij, and Bert van Ulft

Summertime heat waves are extreme meteorological events with a high impact. Three defining aspects are their intensity, duration and spatial extent. All three will change for the worse in a warming world. We illustrate how these changes could play out for the heat wave that produced the hottest day to date in the Netherlands (40.7^◦C, Gilze-Rijen 25 July 2019, a record-shattering event of more than 2 degrees). This is done using a chain of hydrostatic and non-hydrostatic regional climate models of increasing horizontal resolution (12km-2.5km-500m-150m) in combination with the Pseudo Global Warming (PGW) approach. Various scenarios are explored using an ensemble approach to examine robustness. Results indicate that if the 2019 July heat wave were to occur in a +2K warmer world: (i) temperatures would likely reach 45^◦C in many places; (ii) the cumulative heat-wave intensity sum would double; (iii) the time to “cool off” in between heat waves would reduce to a level where the total number of days spent in heat waves roughly equals the number of cool days (Tx<25^◦C); (iv) the area where the 40^◦C threshold is passed will increase strongly; (v) the heat wave will last longer as a simple consequence of the higher temperatures (i.e., an earlier start and a later end). Further persistence increases occur if large-scale circulation changes are supportive; (vi) the temperature response is between 1.5-2 degree per degree global warming, with higher values occurring in scenarios with a stronger future drying. (vii) Finally, during heat waves cities become ‘islands of heat’ where the daily maximum temperatures and the night-time minima are 1-5^◦C higher than in nearby more rural areas. A first impression of these differences is obtained from experimental simulations with the convection permitting model HCLIM43 in ultra-high ‘resolution-of-the-future’ mode (500-150m).

How to cite: de Vries, H., Lenderink, G., van Meijgaard, E., de Rooij, W., and van Ulft, B.: The Dutch heat wave of July 2019 in a warmer world: How much hotter could it get?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7501, https://doi.org/10.5194/egusphere-egu23-7501, 2023.

14:35–14:45

EGU23-15042

ECS

On-site presentation

Extreme Precipitation during Tropical-Extratropical Cloud Bands over South America: comparing observations and Convective-Permitting Model simulations

Marcia Zilli and Neil Hart

Tropical-extratropical cloud bands are typical of the subtropical South American climate, occurring mainly during the rainy season and producing more than 60% of the seasonal precipitation. Thus, their correct representation in climate models is fundamental for the accuracy of simulated subtropical precipitation. Here, we investigate the occurrence of extreme precipitation during tropical-extratropical cloud band events, considering both observed and simulated events. We use outgoing longwave radiation (OLR) data from the National Oceanic and Atmospheric (NOAA) Climate Data Record (CDR) and precipitation from ERA5 reanalysis to identify the observed events. For simulated events, we use the UK Met Office Unified Model convective-permitting simulations considering two different configurations: a control run forced by a high-resolution global climate model (HadGEM3-GC3.1-n512) and a hindcast run forced by a reanalysis product (ERA-Interim) downscaled by an RCM. Both configurations have ten years of data at 4.5 km spatial resolution. The cloud bands are identified using an objective detection algorithm applied to OLR, as described by Zilli and Hart (2021). The convective-permitting simulations reproduce the location and seasonal cycle of observed cloud bands well. To select the extreme cloud band events, we choose the top 20% of events with (a) the most extensive land area with precipitation above a threshold; and (b) the largest average precipitation over the land areas with precipitation above a threshold. Cloud band events that fulfil both these extent and intensity criteria are considered extreme cloud band events. The precipitation threshold is defined as the precipitation rate with the largest fractional contribution to the cloud band's total precipitation over the land area. Extreme cloud band events are responsible for a significant fraction of the seasonal precipitation, with the largest precipitation rates occurring over subtropical latitudes. They occur throughout the cloud band season (NDJFM) but are more frequent during its onset (ND), particularly when considering only the transient ones (i.e., those events persisting less than three days). During persistent extreme cloud band events (i.e., those lasting for four or more days), the moisture anomalies are located mainly over Eastern Brazil and the adjacent tropical South Atlantic Ocean, with a similar but more intense than during all persistent events. On the other hand, transient extreme cloud band events are more dependent on the moisture from the western subtropical South Atlantic Ocean when compared to all transient events. The convective-permitting simulations adequately reproduce the ERA5 precipitation during the extreme cloud band events, despite biases in the intensity of the rain increasing the precipitation threshold values. Despite that, the convective-permitting simulations better represent the precipitation and extremes over subtropical latitudes, providing a valuable tool for improving the understanding and forecasting of cloud band-related extreme precipitation events.

How to cite: Zilli, M. and Hart, N.: Extreme Precipitation during Tropical-Extratropical Cloud Bands over South America: comparing observations and Convective-Permitting Model simulations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15042, https://doi.org/10.5194/egusphere-egu23-15042, 2023.

14:45–14:55

EGU23-15059

On-site presentation

Evaluation of precipitation variability over the Sierra de Guadarrama

Jesús Fidel González-Rouco, Emilio Greciano-Zamorano, Félix García-Pereira, Cristina Vegas-Cañas, Jorge Navarro-Montesinos, Elena García-Bustamante, Ernesto Rodríguez-Camino, and Esteban Rodríguez-Guisado

Heterogeneity in the occurrence, amount, and distribution of precipitation in mountainous areas is relevant for water resources and stresses the need for high-altitude observations and high-resolution modeling over complex terrain. However, the harsh weather conditions and the complex terrain associated with these environments hinder a continuous monitorization and pose challenges for regional climate models.

In this work, data from 37 stations located in the Sierra de Guadarrama and nearly lowlands, in Central Spain, and with altitudes ranging from 600 to 2200 m.a.s.l. have been studied. A few of the highest altitude sites belong to GuMNet facility (https://www.ucm.es/gumnet) and the rest to the Spanish Meteorological Agency (AEMET; https://www.aemet.es). These data have been compared to ERA5 reanalysis (https://confluence.ecmwf.int/display/CKB/ERA5) and to three different resolution (9, 3, and 1 km) outputs of a simulation of the regional climate model WRF (https://www.mmm.ucar.edu/WRF) during the period from 1990-2019. The comparison of the different data sources aims at characterizing the precipitation distribution over the area, assessing the goodness of ERA5, and the potential added value of the increasing resolution of WRF simulation in reproducing the observations.

Results show that the increase in WRF resolution from 9 to 3 km always produces a better representation of precipitation, whereas the step from 3 to 1 km shows a significant improvement at the highest altitudes, but an overestimation of precipitation at low plain areas. The lack of added value in the simulation at the highest resolution is discussed in relation to the parameterization of cumulus precipitation. Also, an altitudinal gradient of precipitation is observed and can be traced to large-scale precipitation.

How to cite: González-Rouco, J. F., Greciano-Zamorano, E., García-Pereira, F., Vegas-Cañas, C., Navarro-Montesinos, J., García-Bustamante, E., Rodríguez-Camino, E., and Rodríguez-Guisado, E.: Evaluation of precipitation variability over the Sierra de Guadarrama, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15059, https://doi.org/10.5194/egusphere-egu23-15059, 2023.

14:55–15:15

EGU23-6121

solicited

On-site presentation

Modeling present-day and future extreme events in the Lake Victoria Basin

Nicole van Lipzig, Jonas Van de Walle, Matthias Demuzere, Andreas H. Fink, Patrick Ludwig, Grigory Nikulin, Joaquim Pinto, Andreas F. Prein, Dave Rowell, Minchao Wu, and Wim Thiery

The population in the Lake Victoria Basin (LVB) is affected by extreme weather both on land, where flooding regularly occurs and on the lake, where nightly storms often catch fishermen by surprise. The CORDEX Flagship Pilot Study ELVIC investigates how extreme weather events will evolve in this region of the world and to provide improved information for the climate impact community. Here we evaluate the performance of five regional climate models at convection-permitting resolution and present projections for the future using COSMO-CLM in a pseudo global warming approach. Most substantial systematic improvements were found in metrics related to deep convection in convection-permitting models compared to their coarser scale counterparts. For the future, extreme precipitation and wind gusts are expected to increase over the lake due to an thermodynamically induced increase in water vapor whereas the impacts of weaker meso-scale circulation over the lake and stronger thunderstorm dynamics compensate each other. More compound events are expected for the future during which both rainfall and wind gusts are intense. Interestingly, the mean precipitation is strongly affected by uncertainties in large-scale dynamics whereas thermodynamics dominate extreme precipitation. This might imply that uncertainties in future projected extremes are smaller than those in mean precipitation.

How to cite: van Lipzig, N., Van de Walle, J., Demuzere, M., Fink, A. H., Ludwig, P., Nikulin, G., Pinto, J., Prein, A. F., Rowell, D., Wu, M., and Thiery, W.: Modeling present-day and future extreme events in the Lake Victoria Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6121, https://doi.org/10.5194/egusphere-egu23-6121, 2023.

Posters on site: Wed, 26 Apr, 16:15–18:00 | Hall X5

Chairpersons: Merja Tölle, Edmund Meredith

X5.248

EGU23-3745

Fluctuations of snow depth before AMeDAS in the foothill area of the Northern Japan Alps

(withdrawn)

Keisuke Suzuki

X5.249

EGU23-296

ECS

Summer winds over the Iberian Peninsula related to thermal low conditions from COSMO-REA6 (1995-2018) high-resolution reanalysis

María Ortega, Enrique Sánchez, Claudia Gutiérrez, Noelia López-Franca, Miguel Ángel Gaertner, and María Ofelia Molina

Thermal low pressure systems are typically generated over continental mid-latitudes and subtropical regions during summer, related to a strong heating over land caused by the long lasting solar radiation during this part of the year. They present a clear diurnal cycle, being more intense during the afternoon, and weakens at nighttime. In Europe, a thermal low forms frequently over the Iberian Peninsula. As strong pressure gradients are generated from the coastal regions to the interior of the Peninsula, wind characterization is a relevant feature to describe the Iberian thermal low. In particular, wind typically enters from the north (the Basque Country) and the east (the Mediterranean coast of Murcia and Valencia) through gaps between mountain ranges, and move respectively in a southwestward or westward direction. In the northern area, the wind flows into the regions of Burgos and Valladolid after channeling across the Duero valley, while in the southeast it reaches a large part of Castilla-La Mancha and even Extremadura. These winds are known in the Iberian Peninsula, for example, the regional wind from the Mediterranean to the Castilla-La Mancha plateau is typically named as Solano. Nevertheless, no systematic effort has been made to fully characterize and quantify its frequency or intensity, so no objective thresholds of wind speed, direction or spatial extension have been defined so far. A first effort to define such objective values is then proposed here. Hourly 10-m wind and 2-m specific humidity fields from COSMO-REA6 very high resolution (0.055º) reanalysis covering the 1995-2018 period are used. This high resolution, both temporal and spatial, will allow us to inspect the orographic aspects that seem to be relevant for these regional winds, together with its clear diurnal cycle and the moisture transport from coastal to inner regions. Humidity is a relevant variable for characterizing these flows, as there are marked differences between the moist air entering from the sea and the dry summer air characteristic of the inner regions of the Iberian Peninsula. The climatic perspective allows to study if interannual variability or trends are also relevant. First results indicate that these regional winds, with mean hourly speeds above 5 m/s for several hours per day, appear during most of the summer days, with important variations in spatial extension and strength. Strong moisture gradients are frequently observed during such episodes. Maximum speed and humidity jumps occur during the afternoon. This analysis is just a starting point, which will be followed by a deeper examination of these flows.

How to cite: Ortega, M., Sánchez, E., Gutiérrez, C., López-Franca, N., Gaertner, M. Á., and Molina, M. O.: Summer winds over the Iberian Peninsula related to thermal low conditions from COSMO-REA6 (1995-2018) high-resolution reanalysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-296, https://doi.org/10.5194/egusphere-egu23-296, 2023.

X5.250

EGU23-15381

Spatiotemporal variability of temperature in Friuli-Venezia Giulia (north-eastern Italy)

(withdrawn)

Tommaso Caloiero, Ilaria Cianni, Roberto Gaudio, Nicola Ricca, and Ilaria Guagliardi

X5.251

EGU23-13414

ECS

Spatial and temporal patterns of tropical forest microclimate in Mount Kenya

Jinlin Jia, Alice C. Hughes, Erone Ghizoni Santos, Petri K.E. Pellikka, and Eduardo Eiji Maeda

Tropical-mountane forests are global biodiversity hotspots, and also play important roles in regional hydrological systems. Yet, climate and especially microclimate in these areas, and how they vary spatially and temporally have been largely neglected. Due to the buffering effect of vegetation, microclimate (i.e. environmental conditions experienced by organisms inside the forest) can be substantially different from the conditions outside the forests. Additionally, sparse meteorological stations and satellite data cannot provide accurate climate estimates over tropical mountains, especially on microclimate under the canopy. Consequently, further research is needed to clarify the spatial and temporal patterns of environmental conditions in these regions.

In this study, we set 16 microclimate sensors on the southern and southeastern slopes of Mount Kenya, with an elevation range of 720 m (from 1730 m a.s.l. to 2450 m a.s.l) across the Lower Montane Wet Forest. The sensors measured understory air temperature and soil moisture every 15-minutes across a 2-year period.

We found that average soil moisture in the study area varied with monthly precipitation, synchronously increasing with the start of the rainy seasons, but decreasing with a approximate one month lag towards the dry seasons. Soil moisture did not have a linear relationship with altitude, presenting a local minimum at about 2050 m a.s.l.. The understory air temperature changed linearly with altitude, whereas the lapse rate varied across seasons. The seasonal variation of diurnal lapse rate was about three times larger than that during the night. For the intra-daily temperature, minimums occured simultaneouly (at 4:30 am) independently of altitude. Conversely, at higher altitudes, the maximum temperature occurred earlier. The lowest average daily temperature and smallest daily temperature range occurred between June and August, whilst the opposite phenomena occurred from January to March. Furthermore, Jan-Feb-Mar also presented the smallest lapse rate and low soil moisture, representing the main period of vegetation growth. Our results will contribute for clarifying the conditions sustaining the disproportionally high biodiversity and biomass observed in tropical mountain forests. Further research will investigate the drivers and biophysical feedbacks of microclimate, as well as their sensitivity to climate change.

How to cite: Jia, J., Hughes, A. C., Santos, E. G., Pellikka, P. K. E., and Maeda, E. E.: Spatial and temporal patterns of tropical forest microclimate in Mount Kenya, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13414, https://doi.org/10.5194/egusphere-egu23-13414, 2023.

X5.252

EGU23-3481

ECS

Dryland land crop yield sensitivity to drought in Botswana: Development ofstatistical tools based on satellite remote sensing, observation and climate models foruse in risk assessment

Tshepho Matsuokwane Manyothwane and Gizaw Mengistu Tsidu

Abstract
Assessing agricultural drought is of great importance as it is viewed as the most serious problem in most
countries in terms of food security, economy, and social stability. Various drought indices have been
developed in order to describe the characteristics of drought such as severity, extent, frequency and
duration. These indices can be classified into two categories: ground-based and remotely-sensed indices.
Ground-based drought indices are more accurate but limited in coverage, while remote sensing drought
indices cover large areas but have poor precision. Therefore there is need to apply advanced data fusion
methods based on satellite data and ground-based drought indices to fill this gap. However there is a lag
time between drought events and the impacts they cause.
Due to the semi arid conditions of Botswana, the country is prone to the occurrence of droughts and has
a great influence on agriculture and economy of the country at large. In order to monitor droughts in
Botswana this paper proposes that it is necessary to link the pre meteorological observations and the
consequential vegetation drought. This is neededed for effective monitoring of agricultural drought and
early warning. In this study, MODIS reflectance data and data from recent satellites such as landsat OLI,
Sentinel will be used to discover relationships between vegetative drought and meteorological drought
using vegetation condition index (VCI) derived from NDVI and NDWI, and meteorological drought
derived from SPI and SPEI in Botswana. Dataset derived from Soil Moisture Active Passive (SMAP)
will be used to generate %soil moisture content. The %moisture content will be compared with
experimental results from the field. Pearson correlation analyses were performed between single remote
sensing drought indices and in-situ drought indices, NDVI and SPEI. Preliminary studies show that VCI
derived from NDWI (VCI-2) over Southern District of Botswana can be used as an approach to monitor
and provide early warnings. However, there is weak correlation SPEI and VCI-1 and VCI-2 ranging
from -1 to 0.2.

How to cite: Matsuokwane Manyothwane, T. and Mengistu Tsidu, G.: Dryland land crop yield sensitivity to drought in Botswana: Development ofstatistical tools based on satellite remote sensing, observation and climate models foruse in risk assessment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3481, https://doi.org/10.5194/egusphere-egu23-3481, 2023.

X5.253

EGU23-16649

ECS

Mountain climate: one of the multipronged challenges in Ethiopia’s Agriculture

Emnet Negash, Bert Van Schaeybroeck, Piet Termonia, Michiel Van Ginderachter, Kwinten Van Weverberg, Maarten Podevyn, and Jan Nyssen

The Ethiopian highlands are home to more than 90% of the Ethiopian population and constitute for 90% of total area suitable for agriculture (Hurni et al., 2010). The livelihood of 66% of Ethiopia’s population depends on subsistence agriculture, mostly rainfed. Little rainfall variability can therefore cause massive economic loss for farmers reliant on rain-fed agriculture, making differences in wealth among farmers on different sides of the mountain. This study aims at understanding the sub daily distribution of summer rain over the Ethiopian highlands using the ALARO-0 regional climate model at convection-permitting resolution of 4 km. The dependence on factors such as leeward or windward conditions, and elevation are explored to categorize and relate the diurnal cycles of surface variables including precipitation, wind speed, humidity, and temperature. Rainfall occurrence in these mountains is mainly influenced by circulation patterns, orography, surface heating and convection, making its distribution very heterogeneous. Elevation is the most important determinant factor leading to increased average rainfall and rainfall per rainfall event towards higher elevations. Ethiopia’s summer rain exhibits a pronounced diurnal cycle with the highest rainfall occurring during the early afternoon hours (12:00–16:00) and the minimum occurring in the late night (04:00–11:00). Windward average rainfall and rainfall per rainfall event are on average 0.05mm h^-1 and 0.08 mm hr^-1 (respectively) larger than leeward events, except during peak hours when leeward events have 0.05 mm higher average rainfall and rainfall per rainfall event. In contrast to average rainfall events, extreme events in the afternoon are often followed by another peak rainfall event at night. Leeward wind speed features a weak diurnal variation as compared to the strong contrast between day and night for windward wind speed. The diurnal cycles of temperature and humidity start earlier in the morning and recede later than the cycles of wind speed and rainfall. Moreover, rainfall peaks occur earlier in the day at higher elevations, and at night in valleys and in Afar Triangle. The prevalence of windward over leeward event probability, the stark contrast in wind speed diurnal cycle between windward and leeward events, and the early peak hour of dewpoint and air temperature all point towards temperature-induced rather than wind-induced convection. Rainfall-temperature dependence, in other words Clausius-Clapeyron relationship, in the lowlands such as the Afar triangle is however at its lowest due to moisture deficit. These differences are very likely to determine hydrology and vegetation distribution, and farmers economy at large.

How to cite: Negash, E., Van Schaeybroeck, B., Termonia, P., Van Ginderachter, M., Van Weverberg, K., Podevyn, M., and Nyssen, J.: Mountain climate: one of the multipronged challenges in Ethiopia’s Agriculture, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16649, https://doi.org/10.5194/egusphere-egu23-16649, 2023.

X5.254

EGU23-2428

The use of regional climate models for estimating past and future precipitable water vapor and extreme precipitation over Ethiopia

Bert Van Schaeybroeck, Abdisa Kawo, Roeland Van Malderen, and Eric Pottiaux

There exist well known relations between Precipitable Water Vapor (PWV) and extreme rainfall which are of prominent importance in the context of climate change. These relations, however, are mostly established in mid-latitudes and for flat terrain. Ethiopia, however, is located in the tropics and features a complex orography, both of which may modulate these relations. We investigate PWV and extreme precipitation over Ethiopia by use of Regional Climate Models (RCMs) from the Coordinated Regional Climate Downscaling Experiment (CORDEX). We first evaluate the RCMs by comparing their annual PWV cycles with the ones obtained from Global Positioning System observations and reanalysis in the past. Additionally, we focus on the behaviour of PWV before and after a heavy-rainfall event. It is found that there are two characteristic timescales, both for the build-up and for the decline around the event of the heavy precipitation: a timescale of about 2 days and a longer timescale that extends beyond ten days which seems unreported in the literature. The RCMs are capable of reproducing the PWV annual cycle and the spatial variability. However, there is a predominantly dry bias that strongly increases with elevations. The RCMs reproduce well the spatial differences of the PWV anomaly peak during a heavy-rainfall event but overestimate the timescales of build-up and decline. Future PWV-changes scale linearly with the near-surface temperature changes at a rate of 7.7% per degree warming and locally increase up to 40% for the end-of-the-century RCP8.5 scenario. Changes in rainfall extremes, on the other hand, do not follow this trend especially in north-western Ethiopia, potentially caused by an overall decrease in rainfall in that region.

How to cite: Van Schaeybroeck, B., Kawo, A., Van Malderen, R., and Pottiaux, E.: The use of regional climate models for estimating past and future precipitable water vapor and extreme precipitation over Ethiopia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2428, https://doi.org/10.5194/egusphere-egu23-2428, 2023.

X5.255

EGU23-6228

Pseudo-global-warming experiments for West Africa

Beth Woodhams, Peter Knippertz, and Andreas Fink

With a rapidly growing population, West Africa is particularly vulnerable to the effects of climate change. While results from the Coupled Model Intercomparison Project (CMIP) experiments cannot agree on the sign of the end-of-century mean precipitation change over West Africa, there is consistent agreement that the most extreme precipitation events will become more intense. Indeed, an increase in the intensity of the most extreme events has already been observed in rain gauge and satellite datasets. These events are vital to understand since heavy rain can cause flooding as well as resulting property, infrastructure and crop damage, spread of disease and ultimately loss of life.

In West Africa, the majority of rainfall is delivered via Mesoscale Convective Systems (MCSs). Convection associated with the land–sea breeze circulation is also significant along the Guinea Coast. It is well understood that coarse climate models are unable to accurately represent systems on the meso- and local-scale and that high-resolution ‘convection-permitting’ models are required to represent the diurnal cycle, intensity, and organisation of convection. However, such models are expensive to run, especially for the long periods required for climate simulations. One solution is to run pseudo-global-warming (PGW) simulations, where 4D (x,y,z,t) climate ‘deltas’ from CMIP models are added to high-resolution reanalysis. The resulting dataset is then used as a boundary condition for high-resolution model runs of case study events in the future climate. In this work, the ERA5 reanalysis is used as the base, and the simulations are performed using the ICOsahedral Nonhydrostatic (ICON) model.

Initial results from bespoke PGW case studies for West Africa will be presented to show how the character of present-day extreme events might change if they were to occur in a future climate. In particular, the work will look at the thermodynamic and dynamic contributions to changes in intensity. Furthermore, changes in storm evolution, propagation and organisation will be analysed.

How to cite: Woodhams, B., Knippertz, P., and Fink, A.: Pseudo-global-warming experiments for West Africa, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6228, https://doi.org/10.5194/egusphere-egu23-6228, 2023.

X5.256

EGU23-12221

ECS

Applying a scaling approach for extreme precipitation to disentangle thermodynamic and dynamic contributions to CORDEX-FPS simulations

Nicole Ritzhaupt, Stefan P. Sobolowski, and Douglas Maraun and the the CORDEX Flagship Pilot Study on Convection over Europe and the Mediterranean – ensemble

The response of the hydrological cycle to global warming is one of the greatest concerns of climate change. Especially, extreme precipitation can lead to severe physical and economic impacts on human and natural systems. Though extreme precipitation is expected to increase over many land areas an important question remains: which factors drive the uncertainty in extreme precipitation? Answering this will help better understand, prepare for, and ultimately, predict future extreme precipitation.

In this study, we use a scaling approach for extreme precipitation events developed by O’Gorman and Schneider (2009) to disentangle the thermodynamic and dynamic contributions to these events. Extreme precipitation is scaled by the vertical integral over the product of the vertical velocity (ω; dynamic contribution) and the derivation of the saturation specific humidity (; thermodynamic contribution): .

We apply this scaling approach to a subset of the CORDEX-FPS ensemble and focus on change signals of seasonal extremes of daily precipitation for two 10-year periods (2090-2099 vs 1996-2005). By keeping either the first term or the second term in the formula constant over the entire time period we obtain the thermodynamic and dynamic signal, respectively. The thermodynamic signal is quite homogeneous over the domain, approximately in the order of Clausius-Clapeyron scaling (~ 7%/K), while the dynamic signal modifies the thermodynamic signal. Thus, the dynamic contribution, which is represented by vertical wind, is key in understanding differences between models and uncertainty in precipitation changes. The vertical wind profiles show, especially for summer, that the vertical winds during extreme events weaken in the future period compared to the historical period. This seemingly counterintuitive result could be due to more downdrafts leading to extreme precipitation in the future period instead of updrafts. However, a comprehensive interpretation is the subject of ongoing research.

How to cite: Ritzhaupt, N., Sobolowski, S. P., and Maraun, D. and the the CORDEX Flagship Pilot Study on Convection over Europe and the Mediterranean – ensemble: Applying a scaling approach for extreme precipitation to disentangle thermodynamic and dynamic contributions to CORDEX-FPS simulations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12221, https://doi.org/10.5194/egusphere-egu23-12221, 2023.

X5.257

EGU23-3516

Improved bias-adjustment methods for subdaily precipitation extremes

Hans Van de Vyver, Bert Van Schaeybroeck, Lesley De Cruz, Rafiq Hamdi, and Piet Termonia

Extreme precipitation events are responsible for severe damage to various aspects of human society and ecosystems. Short-term extremes especially affect people in urban areas through flash floods. Extremely heavy precipitation is increasing in frequency and intensity due to global warming and Regional Climate Models (RCMs) of high-resolution are needed to estimate associated increased risks. However, even the RCMs that explicitly resolve deep convection are known to significantly underestimate subdaily precipitation extremes. Impact modellers and other users of climate projections therefore often use some form of bias correction.

In this study, we propose bias adjustment methods especially designed for the estimation of future subdaily extreme precipitation return levels. These methods take into account the scaling intensity-duration-frequency (IDF) relationship between different levels of accumulation, and jointly estimate extreme rainfall over multiple rainfall durations (i.e. from hourly to multi-day extreme precipitation events). After comparison with established methods, we identify only one method that preserves the scaling IDF relationship, which is a necessary condition to have bias-adjusted return levels consistent among the different durations. A comparative analysis in a multi-model pseudo-reality setting shows that this method is superior to existing bias adjustment methods.

Finally, future projections of bias-adjusted subdaily precipitation return levels for Belgium are obtained in the form of an ensemble of 28 EURO-CORDEX simulations at 0.11° spatial resolution, under the RCM8.5 emission scenario.

How to cite: Van de Vyver, H., Van Schaeybroeck, B., De Cruz, L., Hamdi, R., and Termonia, P.: Improved bias-adjustment methods for subdaily precipitation extremes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3516, https://doi.org/10.5194/egusphere-egu23-3516, 2023.

X5.258

EGU23-14463

ECS

Spatial correlation scales of rainfall fields as the signature of consistent bias-adjustment procedures for convection-permitting simulations

(withdrawn)

Massimiliano Schiavo, Francesco Marra, Eleonora Dallan, and Marco Borga

X5.260

EGU23-14134

ECS

Impact of orography on sub-daily precipitation upper tail from convection-permitting climate model simulations: a multi-model ensemble perspective

Nathalia Correa Sánchez, Eleonora Dallan, Francesco Marra, Giorgia Fosser, and Marco Borga

Understanding the impact of orography on the probability distribution of extreme precipitation at short (i.e., sub-daily) temporal scales, as well as on extreme-rainfall causative processes, is critical for managing risk from rainfall-triggered natural hazards in mountainous regions. High-resolution convection-permitting models (CPMs) are crucial for this type of analysis since they better represent convective processes key to short-duration extremes.

Here, we assess the ability of multi-model CPM ensemble CORDEX-FPS to represent the upper tail of sub-daily precipitation in a complex-orography region in the Eastern Italian Alps. In this area, different orographic impacts on sub-daily precipitation upper tail were reported at different event durations, and significant temporal trends in precipitation intensity were reported during the last few decades, making it a challenging and interesting test case for CPM simulations. An ensemble of six CPMs with a horizontal grid spacing of ∼2.2 km, driven by ERA-Interim reanalysis, are analysed and evaluated against ∼180 rain gauges. Since CPM simulations are too short (10 years) for analysing extremes using conventional methods, we use a non-asymptotic statistical approach (Simplified Metastatistical Extreme Value, SMEV), which was proven to provide reliable results even using short time records. We explore how the model spread vary with elevation and the ability of the multi-model mean to reproduce the distribution parameters and the extreme quantiles up to 100-year return period at different elevations.

How to cite: Correa Sánchez, N., Dallan, E., Marra, F., Fosser, G., and Borga, M.: Impact of orography on sub-daily precipitation upper tail from convection-permitting climate model simulations: a multi-model ensemble perspective, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14134, https://doi.org/10.5194/egusphere-egu23-14134, 2023.

X5.261

EGU23-8455

ECS

Dynamical representation of extreme precipitation events in storm resolving global climate models within the NextGEMS project

Jonathan Wille and Erich Fischer

The intensity of precipitation extremes across Europe is expected to increase through the 21^st century under a warming climate . Current coarse-resolution global climate models broadly project increased variability of both wet and dry extremes; however, they rely on parametrizations schemes of crucial processes controlling extreme precipitation such as convection. These methods often introduce errors and thereby induced uncertainties in projections of extremes in the water cycle that are relevant for policy makers and infrastructure planning. The need for accurate extreme event information on such extremes became further evident after the July 2021 floods (Ibebuchi, 2022) and summer 2022 record-breaking heatwaves/drought across Western Europe.

The ongoing H2020 Next Generation Earth Modelling Systems (NextGEMS) project aims to address these issues with the development of fully-coupled storm-resolving Earth-System Models. Using some of the first runs of the Integrated Forecast System (IFS) from ECMWF and ICON from MPI-M at 4 km and 5 km horizontal resolution respectively, we examine individual extreme precipitation events across Europe and evaluate their representation against similar analogues in the Copernicus European Regional Reanalysis (CERRA) and observational datasets. The unprecedented high resolution of the fully-coupled Storm-Resolving Models and CERRA allows for an evaluation of precipitation characteristics in complex terrain like the Alps (Hughes et al., 2009) or complex coastlines. We first evaluate the spatial and temporal structure of the events, compare their representation to coarse-resolution GCMs and then examine the potential drivers such as atmospheric river using integrated moisture transport and vertical structure of the low-level jet (Swain et al., 2015).

Hughes, M., Hall, A., & Fovell, R. G. (2009). Blocking in Areas of Complex Topography, and Its Influence on Rainfall Distribution. Journal of the Atmospheric Sciences, 66(2), 508–518. https://doi.org/10.1175/2008JAS2689.1

Ibebuchi, C. C. (2022). Patterns of atmospheric circulation in Western Europe linked to heavy rainfall in Germany: preliminary analysis into the 2021 heavy rainfall episode. Theoretical and Applied Climatology, 148(1), 269–283. https://doi.org/10.1007/s00704-022-03945-5

Seneviratne, S.I., X. Zhang, M. Adnan, W. Badi, C. Dereczynski, A. Di Luca, S. Ghosh, I.

Iskandar, J. Kossin, S. Lewis, F. Otto, I. Pinto, M. Satoh, S.M. Vicente-Serrano, M. Wehner, and B. Zhou, 2021: Weather and Climate Extreme Events in a Changing Climate. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1513–1766, doi:10.1017/9781009157896.013.

Swain, D. L., Lebassi-Habtezion, B., & Diffenbaugh, N. S. (2015). Evaluation of Nonhydrostatic Simulations of Northeast Pacific Atmospheric Rivers and Comparison to in Situ Observations. Monthly Weather Review, 143(9), 3556–3569. https://doi.org/10.1175/MWR-D-15-0079.1

How to cite: Wille, J. and Fischer, E.: Dynamical representation of extreme precipitation events in storm resolving global climate models within the NextGEMS project, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8455, https://doi.org/10.5194/egusphere-egu23-8455, 2023.

X5.262

EGU23-615

ECS

Convection-Permitting Future Climate Simulation Based on SSP3-7.0 Scenario Over the Black Sea Basin

Mehmet Baris Kelebek and Barış Önol

The regional climate models are recently run at grid spacings of 4 km or less, so-called the convection-permitting scale, over different regions of the world. The previous studies highlighted the added value of the convection-permitting simulations, especially in representing the daily and sub-daily precipitation over complex topography. The Black Sea Basin, including the coastal areas of the Black Sea and a broad part of the Anatolian Peninsula, is one of the climate change hot-spots with its complex topographical features and where strong air-sea interactions occur. Previously, this region has become a subject of regional climate modelling studies at horizontal resolutions on the order of 10 km. In this study, we performed a decade-long convection-permitting climate simulation at 3 km horizontal resolution between 2061-2070 based on the SSP3-7.0 greenhouse gas emission scenario over the Black Sea Basin. To this end, we downscaled the last generation CMIP6 MPI-ESM1.2-HR outputs by using the WRF model. The results indicate that the daily 2m mean, minimum, and maximum air temperatures increase in the spring, summer, and autumn by about 3°C compared to the 2005-2014 reference period over the study area. Nevertheless, the increase in the cloud cover suppresses the warming in the winter. In terms of precipitation, the total precipitation amount decreases in spring and summer over the Black Sea Basin. On the other hand, the total precipitation amount increases significantly by about 3 mm/day in winter over the Eastern Black Sea region due to the positive change in evaporation of around 15%. The maximum daily precipitation amount reaches 350 mm over the northeast of Turkey and over the Caucasus. The intensification of the daily precipitation is most pronounced in the coastal subregions of the Black Sea Basin. Furthermore, the results highlight the intensification of sub-daily precipitation in these regions. In particular, the afternoon precipitation increases in autumn over the coastal regions of Turkey.

How to cite: Kelebek, M. B. and Önol, B.: Convection-Permitting Future Climate Simulation Based on SSP3-7.0 Scenario Over the Black Sea Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-615, https://doi.org/10.5194/egusphere-egu23-615, 2023.

X5.263

EGU23-13843

ECS

How does the assessment of extreme precipitation profit from convection permitting climate ensembles?

Marie Hundhausen, Hendrik Feldmann, Regina Kohlhepp, and Joaquim G. Pinto

In response to global warming, an intensification of extreme precipitation has been observed, and models project this trend to continue. Since the return values of extreme precipitation events are regularly used in practice in the form of heavy rainfall hazard products, a reliable update of these products is required. Moreover, for resilient planning a projection of future conditions is urged by practice stakeholders.

A promising tool for projection are convection permitting climate simulations, which have been shown to better represent extreme precipitation events compared to coarser simulations and thus provide higher confidence in future extreme estimates. However, due to the large computation time of convection permitting simulations, evaluations are mostly based on single time slice experiments. Therefore, we explore the potential of an unique transient convection permitting (2.8 km) ensemble with COSMO-CLM regional simulations (1971-2100) over Germany, with four ensemble members driven by MPI-ESM-LR, EC-EARTH, CNRM-CM5, and HadGEM2-ES with the emission scenario RCP8.5. Extreme precipitation is derived over 30-year running time slices and the scales investigated span from hourly to 3-day event duration and return periods from 1 year to 100 years, representing the wide range of events considered for application.

Within the historical period (1971-2005) we found adequate agreement between the simulations and the observation data set KOSTRA with increasing bias with longer event duration. Furthermore, the climate change signal, derived as a relative value with regard to the historical period of the simulation, was found to increase with return period and for shorter durations. Strongest relative changes lie within the range of Clausius-Clapeyron-scaling with global warming. Analysis of the uncertainty revealed a substantial residual standard deviation of the linear approximation of the change signal over global warming, highlighting the benefit of a transient ensemble that enables a more robust estimation of the change signal of extreme events. Moreover, the results indicate an increased variance of future extreme precipitation.

How to cite: Hundhausen, M., Feldmann, H., Kohlhepp, R., and Pinto, J. G.: How does the assessment of extreme precipitation profit from convection permitting climate ensembles?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13843, https://doi.org/10.5194/egusphere-egu23-13843, 2023.

X5.264

EGU23-5185

ECS

Highlight

Linking future Gulf Stream warming and increased European winter precipitation in an eddy-rich model

Eduardo Moreno-Chamarro, Louis-Philippe Caron, Pablo Ortega, Saskia Loosveldt Tomas, Malcolm J. Roberts, Aude Carreric, Amanda Frigola, and Eneko Martín Martínez

This contribution discusses future changes in Gulf Stream temperatures, winter precipitation over northwestern Europe, and their connection. We compare HighResMIP historical and ssp5-8.5 scenario simulations generated with five different configurations of the global coupled model HadGEM3-GC3.1, including one at a pioneering 50-km-atmosphere–1/12°-ocean global resolution. The highest resolution model projects an increase in winter rainfall over Europe outside or to the extremes of multimodel ensembles, such as CMIP6 and HighResMIP, for which both the highest ocean and atmosphere resolutions are essential: on the one hand, only the eddy-rich ocean (1/12°) projects a progressive northward shift of the Gulf Stream and substantial surface warming of the region; on the other, only the 50-km atmosphere translates such warming into strengthened extratropical cyclone activity over the North Atlantic and, hence, increased rainfall over Europe. The results suggest that climate projections relying on traditional ~100-km-resolution models might underestimate climate changes in the North Atlantic and Europe, demonstrating the importance of improved Gulf Stream representation for robust uncertainty estimates of climate risk.

We also present the first results of the STREAM project, which aims to study the role of the ocean mesoscale in driving North Atlantic and European climate variability and predictability. We describe the results of the HighResMIP simulations generated with the EC-Earth global climate model at the T1270-ORCA12 resolution (about 15 km in both the atmosphere and the ocean) and explore the main model biases and response to climate change, as well as the variability in the North Atlantic circulation associated with subpolar oceanic deep mixing.

How to cite: Moreno-Chamarro, E., Caron, L.-P., Ortega, P., Loosveldt Tomas, S., Roberts, M. J., Carreric, A., Frigola, A., and Martín Martínez, E.: Linking future Gulf Stream warming and increased European winter precipitation in an eddy-rich model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5185, https://doi.org/10.5194/egusphere-egu23-5185, 2023.

X5.265

EGU23-4462

ECS

Lagrangian analysis of convective rainfall under different synoptic forcing

Edmund P Meredith, Uwe Ulbrich, and Henning W Rust

Precipitation is commonly analysed from an Eulerian perspective, in which rainfall is considered at a fixed location. Lagrangian analysis of precipitation represents an alternative approach. Here, precipitation objects – for example, convective cells – are identified in a precipitation field and are then tracked through space and time, allowing object properties over the whole life of a convective cell to be collected. This approach offers additional insights into the mechanisms by which convective cells develop and behave across their lifecycle, which would not be evident from standard analysis methods.

In this study, we perform Lagrangian analysis of convective cells under different large-scale circulation regimes. Tracking is based on convection-permitting simulations with the COSMO-CLM at 0.025° resolution over central Europe. All identified precipitation objects are tracked through space and time, collecting cell characteristics for each object, e.g. cell area, intensity, distance travelled, etc. Here we associate precipitation objects with categorical synoptic-scale circulation patterns and compare the cell properties between the different categories.

How to cite: Meredith, E. P., Ulbrich, U., and Rust, H. W.: Lagrangian analysis of convective rainfall under different synoptic forcing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4462, https://doi.org/10.5194/egusphere-egu23-4462, 2023.

Posters virtual: Wed, 26 Apr, 16:15–18:00 | vHall CL

Chairperson: Merja Tölle

vCL.1

EGU23-13995

Climate change scenarios for IDF curves for mainland Portugal

Cristina Andrade, Sandra Mourato, Rita Guimarães, and Claúdia Brandão

Rainwater drainage systems and other hydraulic infrastructure are scaled considering the intensity of precipitation and its probability of occurrence. The estimation of precipitation intensity through the analysis of the frequency of occurrence of extreme precipitation events is a key instrument for the dimensioning of hydraulic infrastructures and the associated risk of collapse. Sub- or over-estimated rainfall intensities can cause significant problems in various types of hydraulic infrastructures, including flood mitigation and support works due to flooding.

The aim of this study is to determine how climate change will influence extreme rainfall and, consequently, the future sizing of hydraulic systems, including rainwater drainage and hydraulic passages. Towards this aim, the Intensity-Duration-Frequency (IDF) curves were computed (durations between 24 and 72 hours), considering the historical period between 1950 and 2001, and for future precipitation projections (ensemble of biased-corrected Regional Climate Models, RCMs). The period 2041‒2070 under the RCP8.5 (Representative Concentration Pathways) and 2071‒2100 under the RCP4.5 and RCP8.5 emission scenarios were analyzed for 25 udometric stations studied in Brandão et al. (2001 and 2004) located in mainland Portugal.

Results show an increase in precipitation intensity, however, the differences between the projected IDF and those obtained with observed data (ERA5 dataset) for the 2, 5, 10, 20, 50, and 100 years return periods are not spatially uniform. The outcomes reveal North/South contrasts between the station’s IDFs, being also quite apparent in the influence of the orography.

Overall, this study is the first approach to the problem of extreme rainfall in a changing climate, due to the severe consequences of sudden floods and the resilience of territories and their hydraulic infrastructures to these extreme events. Therefore, planning of new policies and the dimensioning of new and existing infrastructures in the medium and long term is thus highly relevant.

Acknowledgment: This work was supported by National Funds by FCT - Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020.

Keywords: Climate change, IDF curves, Hydraulic passages, Extreme precipitation, Drainage systems, Portugal.

How to cite: Andrade, C., Mourato, S., Guimarães, R., and Brandão, C.: Climate change scenarios for IDF curves for mainland Portugal, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13995, https://doi.org/10.5194/egusphere-egu23-13995, 2023.

vCL.2

EGU23-16986

ECS

The impact of climate change on fire danger over the contiguous United States

Maria Klariza Madrazo, Huikyo Lee, Arezoo Khodayari, Weile Wang, Taejin Park, and Colin Raymond

Recent extreme heat events, especially those that have occurred in the Western United States (WUS), are fueling wildfires and funneling smoke at an unprecedented level, impacting air/water quality and leading to an increase in respiratory hospitalizations. Under greenhouse warming, extreme weather conditions that favor wildfire ignition are expected to occur more frequently over the contiguous United States (CONUS). Therefore, predicting wildfire danger under a changing climate is essential in managing future wildfires and protecting the welfare of people and the environment. In response to mitigating wildfire risks, the Canadian Fire Weather Index (FWI) was developed to provide a numeric rating representing the intensity of a spreading fire. In this work, we utilized fine-scale (0.25° x 0.25°) daily meteorological inputs from thirty-five general circulation models in NASA Earth Exchange Global Daily Downscaled Projections Coupled Model Intercomparison Project Phase 6 (NEX-GDDP-CMIP6) data to calculate the FWI. Using the daily maximum temperature, relative humidity, wind speed, and precipitation from NEX-GDDP-CMIP6, we calculated the FWI of historical and future simulations from the periods of 1950 to 2100 under different emission scenarios (Shared Socioeconomic Pathways 2-4.5 and 5-8.5). We have analyzed the FWI for the GISS-E2-1-G model, which indicates a 2-3% increase per decade in future fire danger under both emission-pathway-driven climate scenarios during the dry season in the Southwestern US. We have found that the FWI climatology in the Southwestern US during the Summer presents high to extreme fire danger (> 50) and higher FWI values in the future compared to historical observations. Moreover, we have explored the uncertainties across multiple models using NEX-GDDP-CMIP6 statistically downscaled data and found a significant spread of the FWI across the models for historical observations and future simulations. To correlate the link between the FWI and actual fire occurrence, we will calculate the FWI using reanalysis data (MERRA-2) and validate the FWI with actual fire occurrence data from Global Fire Emissions Database (GFED) with a special emphasis on the WUS. While supporting the US NCA and NASA’s Climate Adaptation Service Investigator (CASI), we will also try to contribute FWI to NASA’s FireSense, an initiative to bring an Earth systems approach to improving wildfire and wildland fire management.

How to cite: Madrazo, M. K., Lee, H., Khodayari, A., Wang, W., Park, T., and Raymond, C.: The impact of climate change on fire danger over the contiguous United States, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16986, https://doi.org/10.5194/egusphere-egu23-16986, 2023.