Different patterns of climate change scenarios for short-term and multi-day precipitation extremes in the Mediterranean

The study examines climate change scenarios of precipitation extremes over the western, central and part of the eastern Mediterranean region for the late 21st century (2070–99) in an ensemble of high-resolution regional climate model (RCM) simulations from the ENSEMBLES project. Precipitation extremes are considered at a wide range of time scales from hourly to multi-day amounts and in individual seasons (DJF, MAM, JJA, SON). We focus on (1) the dependence of the results on the time scale of precipitation aggregation, (2) seasonal differences, (3) uncertainties of the scenarios related to differences amongst the RCM simulations, and (iv) identification of regions and seasons in which the projected changes in precipitation extremes are particularly large and/or robust in the RCM ensemble.The examined ensemble of RCM simulations captures basic precipitation patterns for the recent climate (1961–90), including seasonal changes. Climate change scenarios for the late 21st century differ substantially for short-term (hourly) and multi-day (5-day and 15-day) precipitation extremes, mainly in the western Mediterranean. Projected increases in short-term extremes exceed those of daily and multi-day extremes, and occur even in regions and seasons in which mean precipitation is projected to decline. This change in the patterns of extreme precipitation may have important hydrological consequences, with increases in the severity of flash floods in a warmer climate in spite of the overall drying projected for the region. However, uncertainty of the scenarios of precipitation extremes related to within-ensemble variability is large. Consistency of the projected changes amongst the RCMs is highest in winter and lowest in summer, and generally it is higher for short-term than multi-day extremes.

► We evaluate climate-change scenarios of precipitation extremes in the Mediterranean based on an ensemble of RCMs. ► Projected increases of short-term precipitation extremes exceed those of multi-day extremes. ► The largest ensemble–mean increases are projected in autumn. ► Increases are simulated even in regions and seasons in which mean precipitation declines. ► The change in precipitation patterns may be manifested also in higher frequency and severity of flash floods.