The basic concept of land-sea temperature contrast and the strength of the Asian summer monsoon is investigated here by comparing the relative contributions of external conditions (involving surface albedo) and internal feedbacks (involving soil moisture) in a number of atmospheric general circulation model (GCM) mean climate simulations and in a GCM sensitivity experiment. All models are run with the same long-term mean sea surface temperatures so that only land-surface conditions affect the land-sea temperature contrast. There is a surprising consistency among the various models such that stronger summer monsoons (defined as high area-averaged precipitation over south Asia) are associated with greater land-sea temperature contrast (i.e., higher land temperatures), lower sea level pressure over land, less snow cover, and greater soil moisture. In a sensitivity study with land albedos uniformly raised from 0.13 to 0.20 in one of the models, the winter-spring-summer sequence over southern Asia shows that there is a high sensitivity to the specified land albedos. Lower land albedos are associated with warmer land temperatures, greater land-sea temperature contrast, and a stronger Asian summer monsoon. There is also a positive feedback between soil moisture and precipitation (increased soil moisture provides a surface moisture source for further precipitation).
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