Global warming impact on rainfall during heavy precipitation events in the eastern Mediterranean

Abstract:

In response to global warming, precipitation is expected to decrease on average in dry regions, but rainfall intensities are projected to increase during extreme events. Heavy precipitation events (HPEs) in the densely populated eastern Mediterranean region supply critical amounts of fresh water to this desert-bounded region. More generally, water resources in semi-arid regions are expected to increasingly depend on the effect global warming would have on rainfall during HPEs. In this study we use a 1 km² resolution (convection-permitting) weather research and forecasting (WRF) model to simulate 41 historical HPEs under ‘pseudo global warming’ based on the mean climate change projected from an ensemble of 29 Coupled Model Intercomparison Project Phase 5 (CMIP5) models for the end of the century. Historic events are identified using a weather radar, and high-resolution spatiotemporal rainfall patterns are compared both with the radar and with historical WRF simulations. In contrast to results from other regions, accumulated rainfall is projected to decrease substantially during HPEs. The meteorological factors leading to this decrease include shallower cyclones and the projected differential land-sea warming, which causes reduced relative humidity over land. These changing rainfall patterns are expected to amplify water scarcity – a known nexus of conflict and strife in the region – highlighting the urgent need for adaptation and mitigation strategies.