Evaluation of flash drought under the impact of heat wave events in southwestern Germany

Menghao Wang; Lucas Menzel; Shanhu Jiang; Liliang Ren; Chong-Yu Xu; Hao Cui

doi:10.1016/j.scitotenv.2023.166815

Evaluation of flash drought under the impact of heat wave events in southwestern Germany

Sci Total Environ. 2023 Dec 15:904:166815. doi: 10.1016/j.scitotenv.2023.166815. Epub 2023 Sep 4.

Authors

Menghao Wang¹, Lucas Menzel², Shanhu Jiang³, Liliang Ren¹, Chong-Yu Xu⁴, Hao Cui⁵

Affiliations

¹ The National Key Laboratory of Water Disaster Prevention, Hohai University, Nanjing 210098, China; Cooperative Innovation Center for Water Safety and Hydro-Science, Hohai University, Nanjing 210098, China; College of Hydrology and Water Resources, Hohai University, Nanjing 210098, China.
² Department of Geography, Professorship in Hydrology and Climatology, Heidelberg University, Heidelberg D-69120, Germany. Electronic address: lucas.menzel@uni-heidelberg.de.
³ The National Key Laboratory of Water Disaster Prevention, Hohai University, Nanjing 210098, China; Cooperative Innovation Center for Water Safety and Hydro-Science, Hohai University, Nanjing 210098, China; College of Hydrology and Water Resources, Hohai University, Nanjing 210098, China. Electronic address: hik0216@hhu.edu.cn.
⁴ Department of Geosciences, University of Oslo, Oslo, Norway.
⁵ College of Hydrology and Water Resources, Hohai University, Nanjing 210098, China.

PMID: 37673262
DOI: 10.1016/j.scitotenv.2023.166815

Abstract

Flash droughts are a recently recognised type of extreme drought defined by the rapid onset and strong intensification of drought conditions. Our understanding of flash drought processes under the influence of heat waves needs to be improved in the context of global warming. Here, we applied a physically based hydrological model, i.e., TRAnspiration and INterception (TRAIN) model to simulate root zone soil moisture (RZSM) and evapotranspiration (ET) with daily time steps and at a 1 × 1 km resolution to identify and assess flash droughts. Two states, Baden-Württemberg (BW) and Rhineland-Palatinate (RP), located in southwestern Germany, were selected as the study areas. Three datasets, the Global Land Evaporation Amsterdam Model (GLEAM) dataset, ERA5-Land (land component of the fifth generation of European ReAnalysis) dataset, and SMAP-L4 (Soil Moisture Active Passive Level-4) dataset, were selected to evaluate the TRAIN simulated RZSM and ET from 1961 to 2016. The results show that the simulated RZSM had the highest correlation with the ERA5-Land products, followed by SMAP-L4 and GLEAM, with regional average correlation coefficients (CC) of 0.765, 0.762, and 0.746, respectively. The CC of the TRAIN simulated ET with ERA5-Land and GLEAM ET were 0.828 and 0.803, respectively. The results of the trend analyses showed a significant increase (p < 0.05) in the number of flash droughts and heat waves in both the BW and RP states. A comparative analysis revealed that the mean duration and onset speed of flash droughts in BW (RP) without heat waves were 10.42 (10.67) pentads and 19.69th percentile/pentad (17.16th percentile/pentad), respectively, while associated with heat waves they were 8.95 (9.53) pentads and 21.77th percentile/pentad (19.91th percentile/pentad), respectively. This indicates that flash droughts under the influence of heat waves are generally shorter in duration but faster in occurrence. The findings of this study have important implications for flash drought assessment, monitoring, and mitigation under the impact of heat waves.

Keywords: Evapotranspiration; Flash drought; Heat waves; Root zone soil moisture; TRAIN model.