Droughts in Germany: performance of regional climate models in reproducing observed characteristics

Abstract

Abstract. Droughts are among the most relevant natural disasters related to climate change. We evaluated different regional climate model outputs and their ability to reproduce observed drought indices in Germany and its near surroundings between 1980–2009. Both outputs of an ensemble of six EURO-CORDEX models of 12.5 km grid resolution and outputs from a high-resolution (5 km) Weather Research and Forecasting (WRF) run were employed. The latter model was especially tailored for the study region regarding the physics configuration. We investigated drought-related variables and derived the 3-month standardized precipitation evapotranspiration index (SPEI-3) to account for meteorological droughts. Based on that, we analyzed correlations, the 2003 event, trends and drought characteristics (frequency, duration and severity) and compared the results to E-OBS. Methods used include Taylor diagrams, the Mann–Kendall trend test and the spatial efficiency (SPAEF) metric to account for spatial agreement of patterns. Averaged over the domain, meteorological droughts were found to occur approximately 16 times in the study period with an average duration of 3.1 months and average severity of 1.47 SPEI units. WRF's resolution and setup were shown to be less important for the reproduction of the single drought event and overall drought characteristics. Depending on the specific goals of drought analyses, computation resources could therefore be saved, since a coarser resolution can provide similar results. Benefits of WRF were found in the correlation analysis. The greatest benefits were identified in the trend analysis: only WRF was able to reproduce the observed negative SPEI trends to a fairly high spatial accuracy, while the other regional climate models (RCMs) completely failed in this regard. This was mainly due to the WRF model settings, highlighting the importance of appropriate model configuration tailored to the target region. Our findings are especially relevant in the context of climate change studies, where the appropriate reproduction of trends is of high importance.

Heat wave characteristics: evaluation of regional climate model performances for Germany

“…To our knowledge, there is no study that presents an evaluation of the EURO-CORDEX RCM's capability to reproduce heat wave characteristics for Germany, which has motivated us to perform this analysis. At the same time this study is the followup to the model comparison study for droughts from Petrovic et al (2022). The thematic proximity is obvious, since heat and drought are often, but not always, related to each other.…”

“…Moreover, we can compare the new core findings for heat waves with those from the aforementioned drought analysis (Petrovic et al, 2022) in terms of similarities and differences.…”

“…resolution were often analyzed, which led to different findings: Zeng et al (2016) and Vichot-Llano et al (2021), for example, found that higher resolution leads to better reproduction of temperature fields, while Di Luca et al (2013) came to the conclusion that the potential for added value of increased resolution is small. It is important to consider the differences between the compared resolutions in such studies (Petrovic et al, 2022). Besides the model resolution, the model setup regarding the domain configuration and physical parameterizations for the selected target region is a crucial factor for reliable simulations (e.g., Stoelinga et al, 2003;Kumar et al, 2010).…”

“…To attribute to a resolution or settings effect of the WRF model performance, we additionally include a 15 km domain configuration in our analysis which is slightly coarser than for the EURO-CORDEX standard. Therefore, following up on the drought study (Petrovic et al, 2022), the objectives of this study are:…”

A satellite view of the exceptionally warm summer of 2022 over Europe

“…The mechanisms involved in feedbacks between these processes are still under debate, not only due to the remaining uncertainties within the theoretical framework but also due to the lack of suitable observations to support it (Miralles et al, 2014Seneviratne et al, 2021;Barriopedro et al, 2023). This means that there is a significant spread in the heatwave metrics that are provided by different global and regional models, even at higher spatial resolutions (Petrovic et al, 2024;Lin et al, 2022;Furusho-Percot et al, 2022;Molina et al, 2020;Hundhausen et al, 2023).…”