"North drying and south wetting" summer precipitation trend over China and its potential linkage with aerosol loading

Changes in summer precipitation over China and their linkage to aerosol loading during 1957-2008 were analyzed. Increased (decreased) summer precipitation has been observed over the Southern (Northern) China, presenting a "north drying and south wetting" pattern. Such a change in precipitation pattern is related to the decreased summertime temperature over South-central China (cool zone). The cool zone, in turn, is likely caused by the increased aerosol loading, as manifested by the increased Aerosol optical depth (AOD) over this region. The cooling effect in the cool zone together with steady warming over adjacent oceans (the South China Sea and the Western North Pacific) weaken land-sea temperature contrast, and thus the East Asia summer monsoon (EASM) circulation. The weakened EASM might restrain the rainbelt in southern China longer with less moisture penetrating further north in summer season. Our analysis suggests that the aerosol loading induced "cool zone" could contribute to the "north drying with south wetting" pattern over Eastern China by altering the intensity of EASM. Furthermore, this change in precipitation pattern is also reflected in the trend of Palmer Drought Severity Index in Eastern China, which indicates a more extensive tendency of dryness in Eastern China by considering both precipitation and temperature.