Impact of initial soil moisture anomalies on climate mean and extremes over Asia

This paper focuses on the impact of soil moisture anomalies on subsequent precipitation and surface air temperature over Asia based on numerical experiments using a regional climate model. Soil moisture anomalies are applied on 1 March, 1 June, and 1 September for the spring, summer, and autumn experiments, respectively, and their impacts on both the climate mean and extremes are examined. Major findings are the following. (1) The land surface memory for soil moisture anomalies is longer in the midlatitudes and shorter in the Tropics, and such memory is enhanced by soil moisture-precipitation feedback. (2) The wet (dry) initial soil moisture anomalies increase (reduce) the subsequent precipitation amount and reduce (increase) surface temperature. For precipitation, the strongest impacts are found in midlatitude to high-latitude regions including northwest China, central Asia, southern Siberia; for temperature, the strongest response is found in India and Indochina regions and most of the midlatitude areas in spring, in high-latitude and midlatitude regions in summer, and in India and eastern China (lower Yellow river basin) in autumn. (3) The impact on mean climate variables can last for 2-3months over most regions of strong response, and the impact of wet initial soil moisture anomalies tends to be stronger but dissipates faster than the dry initial anomalies. (4) Both the dry and wet initial soil moisture anomalies tend to reinforce severe flood extremes, while other climate extremes respond to initial anomalies in a way similar to the mean climate: wet (dry) initial soil moisture anomalies reduce (amplify) the drought extremes, diminish (reinforce) the hot extremes, and enhance (reduce) the cold extremes over areas of strong soil moisture-atmosphere coupling.