Precipitation response to climate change in the Mediterranean region – Forcings & Dynamics

Which forcings and processes govern the projected future drying of the Mediterranean region as CO2 concentrations rise, and how do they interact? An intermediate-complexity moist general circulation model is used to investigate the precipitation response to climate change in the Mediterranean region. In particular, we examine stationary wave changes forced by land–sea contrast, zonal heat fluxes in the ocean, and topography, coupled with a quadrupling of initial CO2 concentrations. Eight different combinations are formed from the three forcings, and the linearity and additivity of the response are investigated. An expected decrease in precipitation over the Mediterranean region is found, accompanied by a strong anomalous ridge, with a significant difference in magnitude between the south-east and north-west of the region, as shown in previous studies. New results suggest that horizontal heat fluxes in the ocean may be a major forcing for future Mediterranean drying, especially over the eastern Mediterranean in winter. The influence of the land-sea contrast is found to be more complex than previously shown, varying from west to east and from north to south of the Mediterranean basin, suggesting further dynamics governing the response in each area. In an attempt to break down the influence of several components of the thermodynamic condition in the Mediterranean, we isolate geographical elements (the Mediterranean, continental Europe , etc.) and examine the precipitation and geopotential height field response, in hope to refine the future projection and better understand the dynamics governing it.