Abstract

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.