Browsing by Person "Warrach-Sagi, Kirsten"

Now showing 1 - 4 of 4

The added value of km-scale simulations to describe temperature over complex orography: the CORDEX FPS-Convection multi-model ensemble runs over the Alps
(2024) Soares, P. M. M.; Careto, J. A. M.; Cardoso, Rita M.; Goergen, Klaus; Katragkou, Eleni; Sobolowski, Stefan; Coppola, Erika; Ban, Nikolina; Belušić, Danijel; Berthou, Ségolène; Caillaud, Cécile; Dobler, Andreas; Hodnebrog, Øivind; Kartsios, Stergios; Lenderink, Geert; Lorenz, T.; Milovac, Josipa; Feldmann, Hendrik; Pichelli, Emanuela; Truhetz, Heimo; Demory, Marie Estelle; de Vries, Hylke; Warrach-Sagi, Kirsten; Keuler, Klaus; Raffa, Mario; Tölle, Merja; Sieck, Kevin; Bastin, Sophie
The increase in computational resources has enabled the emergence of multi-model ensembles of convection-permitting regional climate model (CPRCM) simulations at very high horizontal resolutions. An example is the CORDEX Flagship Pilot Study on “Convective phenomena at high resolution over Europe and the Mediterranean”, a set of kilometre-scale simulations over an extended Alpine domain. This first-of-its-kind multi-model ensemble, forced by the ERA-Interim reanalysis, can be considered a benchmark dataset. This study uses a recently proposed metric to determine the added value of all the available Flagship Pilot Study hindcast kilometre-scale simulations for maximum and minimum temperature. The analysis is performed using state-of-the-art gridded and station observations as ground truth. This approach directly assesses the added value between the high-resolution CPRCMs against their driving global simulations and coarser resolution RCM counterparts. Overall, models display some modest gains, but also considerable shortcomings are exhibited. In part, these deficiencies can be attributed to the assimilation of temperature observations into ERA-Interim. Although the gains for the use of kilometre-scale resolution for temperature are limited, the improvement of the spatial representation of local atmospheric circulations and land–atmosphere interactions can ultimately lead to gains, particularly in coastal areas.
The added value of simulated near-surface wind speed over the Alps from a km-scale multimodel ensemble
(2024) Molina, M. O.; Careto, J. M.; Gutiérrez, C.; Sánchez, E.; Goergen, K.; Sobolowski, S.; Coppola, E.; Pichelli, E.; Ban, N.; Belus̆ić, D.; Short, C.; Caillaud, C.; Dobler, A.; Hodnebrog, Ø.; Kartsios, S.; Lenderink, G.; de Vries, H.; Göktürk, O.; Milovac, Josipa; Feldmann, H.; Truhetz, H.; Demory, M. E.; Warrach-Sagi, Kirsten; Keuler, K.; Adinolfi, M.; Raffa, M.; Tölle, M.; Sieck, K.; Bastin, S.; Soares, P. M. M.
The advancement of computational resources has allowed researchers to run convection-permitting regional climate model (CPRCM) simulations. A pioneering effort promoting a multimodel ensemble of such simulations is the CORDEX Flagship Pilot Studies (FPS) on “Convective Phenomena over Europe and the Mediterranean” over an extended Alps region. In this study, the Distribution Added Value metric is used to determine the improvement of the representation of all available FPS hindcast simulations for the daily mean near-surface wind speed. The analysis is performed on normalized empirical probability distributions and considers station observation data as the reference. The use of a normalized metric allows for spatial comparison among the different regions (coast and inland), altitudes and seasons. This approach permits a direct assessment of the added value between the CPRCM simulations against their global driving reanalysis (ERA-Interim) and respective coarser resolution regional model counterparts. In general, the results show that CPRCMs add value to their global driving reanalysis or forcing regional model, due to better-resolved topography or through better representation of ocean-land contrasts. However, the nature and magnitude of the improvement in the wind speed representation vary depending on the model, the season, the altitude, or the region. Among seasons, the improvement is usually larger in summer than winter. CPRCMs generally display gains at low and medium-range altitudes. In addition, despite some shortcomings in comparison to ERA-Interim, which can be attributed to the assimilation of wind observations on the coast, the CPRCMs outperform the coarser regional climate models, both along the coast and inland.
A multivariate approach to drought monitoring: Improving robustness and accuracy through a new drought index in regions with high climate variability, applied to the drought-prone region of Ethiopia
(2026) Kebede, Abebe; Warrach-Sagi, Kirsten; Schwitalla, Thomas; Wulfmeyer, Volker; Abebe, Tesfaye; Tadesse, Tsegaye
Study focus: Assessing, monitoring, and quantifying drought characteristics to develop early warning systems is crucial for identifying the spatial extent and severity of droughts at regional and local scales especially in regions of vulnerable societies relying on local agriculture. Observations and reanalysis from 1981 to 2022 are analyzed for spatiotemporal droughts in Ethiopia. While standard drought indices like Standardized Precipitation Index and Standardized Soil Moisture Index are based solely on precipitation or soil moisture, a new drought index based on precipitation, potential evaporation, surface temperature, soil temperature, and soil moisture is developed, making the index more robust to climate and land use changes. This new Multivariate Standardized Drought Index (MvrSDI) is evaluated focusing on the severity and duration of 2015 and 2022 droughts in Ethiopia. Results show that spatiotemporal comparisons of MvrSDI at 3-, 6-, and 12-month time scales detect drought severity and duration in each drought-prone region of Ethiopia. Further,Mann-Kendall statistic test identifiy a drought trend between 1981 and 2022 an increasing drought severity. New hydrological insight for the region: The MvrSDI effectively assesses and monitors drought impacts on agriculture, proving beneficial for stakeholders focused on environmental sustainability and food security. Its multivariate character makes MvrSDI more robust and therefore a valuable tool for drought monitoring and decision-making in regions with high climate variability and land use changes in drought-prone regions like Ethiopia.
Soil moisture–atmosphere coupling strength over central Europe in the recent warming climate
(2025) Schwitalla, Thomas; Jach, Lisa; Wulfmeyer, Volker; Warrach-Sagi, Kirsten
In recent decades Europe has experienced severe droughts and heatwaves. Notably, precipitation in central Europe exhibited strong dry anomalies during the summers of 2003, 2018, and 2022. This phenomenon has significant implications for agriculture, ecosystems, and human societies, highlighting the need to understand the underlying mechanisms driving these events. Despite significant advancements in understanding land–atmosphere (LA) coupling, the temporal variability in LA coupling strength and its associated impacts remain poorly understood. This study aims to quantify the variability in LA coupling strength over central Europe during the summer seasons from 1991 to 2022, with a focus on the relationships between temperature, soil moisture, precipitation, and large-scale weather patterns. Our results reveal that interannual variability occurs in different coupling relationships throughout the summer seasons, with significant implications for climate extremes, agriculture, and ecosystems. The increasing frequency of warm and dry summers from 2015 onwards hints at extended periods of reduced soil moisture available for evapotranspiration and the likelihood of locally triggered convection. This study provides new insights into the dynamics of LA coupling, highlighting the importance of considering the interannual variability in LA coupling strength in climate modeling and prediction, particularly in the context of a warming climate.