Abstract
Abstract. Future climate scenarios for the Mediterranean region indicate a possible decrease in annual precipitation associated with an intensification of extreme rainfall events in the coming years. A major challenge in this region is to evaluate the impacts of changing precipitation patterns on extreme hydrological events such as droughts and floods. For this, it is important to understand the impact of climate change on soil moisture since it is a proxy for agricultural droughts, and the antecedent soil moisture condition plays a key role on runoff generation. This study focuses on 10 sites, located in southern France, with available soil moisture, temperature, and precipitation observations for a 10-year time period. Soil moisture is simulated at each site at the hourly time step using a model of soil water content. The sensitivity of the simulated soil moisture to different changes in precipitation and temperature is evaluated by simulating the soil moisture response to temperature and precipitation scenarios generated using a delta change method for temperature and a stochastic model (the Neyman–Scott rectangular pulse model) for precipitation. Results show that soil moisture is more impacted by changes in precipitation intermittence than precipitation intensity and temperature. Overall, increased temperature and precipitation intensity associated with more intermittent precipitation leads to decreased soil moisture and an increase in the annual number of days with dry soil moisture conditions. In particular, a temperature increase of +4 ∘C combined with a decrease of annual rainfall between 10 % and 20 %, corresponding to the current available climate scenarios for the Mediterranean, lead to a lengthening of the drought period from June to October with an average of +28 d of soil moisture drought per year.
Highlights
The Mediterranean region is a transitional zone between dry and wet climates, and in these semiarid areas the direct evaporation from the soil plays an important role on the surface energy balance, with evapotranspiration strongly dependent on available soil moisture (Koster et al, 2004; Seneviratne et al, 2010; Taylor, 2015)
Convectionpermitting regional climate models (CPRCMs) have been increasingly implemented over Europe in recent years to reproduce hourly changes in precipitation (Coppola et al, 2018) and these simulations should be considered in future experiments
Future climate scenarios for the Mediterranean indicate an increase in temperature associated with an increased frequency of dry days and an intensification of extreme rainfall events
Summary
The Mediterranean region is a transitional zone between dry and wet climates, and in these semiarid areas the direct evaporation from the soil plays an important role on the surface energy balance, with evapotranspiration strongly dependent on available soil moisture (Koster et al, 2004; Seneviratne et al, 2010; Taylor, 2015). The water contained in the unsaturated, or vadose zone, is an important driver for floods with soils close to saturation having more probability to produce runoff when subjected to precipitation inputs (Zehe et al, 2005; Ivancic and Shaw, 2015; Woldemeskel and Sharma, 2016; Bennett et al, 2018; Wasko and Nathan, 2019) This is true in the Mediterranean context where several studies have shown the strong influence of soil moisture on flood generation processes (Brocca et al, 2008; Penna et al, 2011; Tramblay et al, 2010, 2019; Uber et al, 2018).
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