Early Summer Soil Moisture Contribution to Western European Summer Warming

Abstract

AbstractWarm European summer temperatures are often preceded by low soil moisture conditions, but also depend on the atmospheric circulations and associated rainfall that may trigger drought to persist and land‐atmosphere feedbacks to take place. The quantitative role of early summer soil moisture (ESSM) trends, versus that of trends in atmospheric circulations and other large‐scale drivers (LS), in explaining the long‐term trends in summer warming have not been investigated so far. Using regional climate simulations with forced large‐scale circulation and different possible initial soil moisture, we show that the increasing ESSM deficit explains almost all of the warming summer trend (1980–2011) in Western Europe (∼0.1–0.2°C.decade−1, p‐value < 0.05). It also contributed a similar amount to summer warming trend in Eastern Europe, although here LS explains a much larger part of the overall warming. Our results emphasize the crucial role of the pre‐summer water cycle in current and future regional evolutions of Western European summer climate.