Extreme dry spells over the Mediterranean Basin during the wet season: Assessment of HyMeX/Med‐CORDEX regional climate simulations (1979–2009)

Abstract

Exceptional dry spells, in this study referred to as very long dry spells (VLDS), are natural hazards to which the Mediterranean region is extremely vulnerable, with socio-economic and environmental impacts. In this study, they are characterized in terms of location, spatial extent, duration, temporal variability and associated atmospheric circulations. The main objective is to assess the performance of five HyMeX/Med-CORDEX regional climate simulations to detect and reproduce VLDS in comparison with the E-OBS observed daily gridded data. Models accurately reproduce the occurrence of precipitation around the Mediterranean Basin, and therefore the occurrence of VLDS, with at least 51% of the E-OBS VLDS reproduced by the regional simulations. They also accurately simulate the spatiotemporal characteristics. A second objective is to identify the synoptic atmospheric patterns associated with VLDS. A clustering analysis shows that all models accurately reproduce the main VLDS spatial patterns, associated with anticyclonic conditions above the affected regions. The simulated VLDS occurrence is strongly related to the amplitude of the sea level pressure and 500-hPa geopotential height anomalies as well as the location of the maximum anomalies. All VLDS events are associated with anticyclonic conditions except those occurring in the eastern Mediterranean, where they are generally not associated with a specific meteorological event but with the usual summer weather regime.

Evaluation of CORDEX Regional Climate Models in Simulating Extreme Dry Spells in Southwest China

“…For the five RCMs used in this study, the four RCMs besides YSU-RSM reproduced the spatial pattern of the proportion of dry days and the climatology of the AMDSL over the SWC region. This is consistent with the previous results of RCM simulations on different regional scales (Tebaldi et al, 2006;Sushama et al, 2010;Wehner et al, 2010;Raymond et al, 2016Raymond et al, , 2018Tramblay and Hertig, 2018). It should be noted that large spatial variability differences are found among different RCM simulations.…”

“…Threshold for the AMDSL In this study, following previous studies (Frich et al, 2002;Sushama et al, 2010;Raymond et al, 2016Raymond et al, , 2018Tramblay and Hertig, 2018), an annual maximum dry spell length (AMDSL) is defined as the largest number of consecutive days without precipitation or with precipitation less than 1 mm/day, a threshold also adopted to identify CDD by the Expert Team on Climate Change Detection and Indices (ETCCDI) . The choice of this threshold is subjective and has been used in most previous studies on CDD or AMDSL on a global and regional scale (Sushama et al, 2010;Donat et al, 2016;Raymond et al, 2016;Herold et al, 2017).…”

“…They also found those RCMs tend to underestimate the extreme dry spell frequency over wetter regions of the Mediterranean Basin. Raymond et al (2018) used HyMeX/Med-CORDEX experiments to detect very long dry spells (VLDS) over the Mediterranean Basin. They found that at least 51% of the observed VLDS were reproduced by the RCM simulations and that those RCMs accurately simulated spatiotemporal characteristics.…”

Comparison of statistical downscaling methods for climate change impact analysis on drought

“…For Europe, extreme dry spells have become shorter in the North (Scandinavia and parts of Germany) and longer in the Netherlands and the central parts of France and Spain. Using climate model data, Raymond et al (2018Raymond et al ( , 2019 found a future evolution towards longer dry spells and a larger spatial extent of extreme dry spells in the Mediterranean basin. For Belgium, Tabari et al (2015) studied future water availability by comparing precipitation and potential evapotranspiration.…”

A Stochastic Approach for the Analysis of Long Dry Spells with Different Threshold Values in Southern Italy

“…In southern Africa, dry spells have been analyzed using gridded data by Usman and Reason [29]. Concerning the Mediterranean Basin, Raymond et al [30] analyzed extreme dry spells during the wet season. Schmidli and Frei [31] investigated the trends of heavy precipitation and wet and dry spells in Switzerland during the 20 th century at a seasonal time scale based on daily precipitation data at 104 gauge stations.…”