Abstract:Influenced by many climatic factors,the precipitation anomaly over the Maritime Continent (MC) shows strong regional features.Based on the NCEP/NCAR,GPCP and GODAS monthly mean reanalysis data from the period of 1979 to 2013,in this study we investigated the regional characteristics of precipitation in the Indian Ocean side of the MC,as well as the relationships between different precipitation patterns with variations of the East Asian monsoon and tropical circulation,using regression and other statistical methods.The results show that one oceanic area to the west of Java Island (Box-A),and another in the equatorial Indian Ocean to the west of Sumatra (Box-B),are two key regions where the precipitation varies inter-annually with larger variance in the west of the MC.It is found that there are significant differences in the rainfall variation in Box-A from that in Box-B,although the rainfall variations between these two key regions are significantly correlated.When the summer precipitation is abnormally high in these two areas,the water vapor from the equatorial Indian Ocean,equatorial Pacific,South China Sea and Bay of Bengal is strong.However,precipitation in Box-A is closely related to the IOD mode,while that in Box-B has a closer relationship with monsoon activities.When the precipitation anomalies in Box-A are positive,the warm sea water in the mixed layer converges to Box-A to sustain the higher than normal SST in this area,thereby facilitating an anomalous cyclonic circulation over Box-A and its southwestern side to the Box-A in the lower troposphere.This warmer SSTA,along with the cyclonic circulation,are responsible for the anomalous upward motion and greater precipitation there.When the precipitation is abnormally high over Box-B,the anomalous circulation appears similar to that in Box-A,albeit slightly weaker and more westward.The warmer SST in Box-B is mainly related to the upwelling anomalies in the ocean.All of these results are helpful for our better understanding of the mechanisms of variations of both regional climate in the MC and the Asian summer monsoon anomalies.