Browsing by Person "Warrach-Sagi, Kirsten"

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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.
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.