Drier Mediterranean soils due to greenhouse warming bring easterly winds over summertime central Europe

Western European summers become more continental in simulations for the 21st century. Anomalously large summer warming over the Mediterranean area in concert with drier soils and a reduced surface pressure can explain this change. The warming is enhanced due to soil moisture depletion which limits the cooling of the land surface by evaporation. A large-scale Mediterranean heat low develops, bringing easterly winds over Central Europe. Statistical analysis for present-day conditions indicates that the same mechanism operates on intra-seasonal timescales; dry Mediterranean soils in June are correlated with high temperature and low surface pressure in July-August. Idealized simulations confirm the relation between the surface warming of the Mediterranean area and the development of a heat low. The development of a heat low in response to dry soils induces a positive feedback: drier Mediterranean soils in summer bring easterly winds over Europe and increase the continental character of Western European summer climate. Citation: Haarsma, R. J., F. Selten, B. vd Hurk, W. Hazeleger, and X. Wang (2009), Drier Mediterranean soils due to greenhouse warming bring easterly winds over summertime central Europe, Geophys. Res. Lett., 36, L04705, doi: 10.1029/2008GL036617.