Influences of spring-to-summer SSTs over different Indian Ocean regions on the Asian summer monsoon: A numerical study

Abstract:

The influences of spring-to-summer sea surface temperature (SST) anomalies in different regions of the Indian Ocean (IO) on the summer climate over the Asian monsoon region is investigated by conducting a series of numerical experiments using the NCAR CAM4 model. It is observed that to a certain extent the spring SST anomalies of regional IO SST maintain to the summer season. The spring-to-summer IO SST anomalies associated with the Indian Ocean basin warming mode have a strong link to the summer climate over Asia, especially the South Asian monsoon (SAM) and the East Asian monsoon. Among this link, the warming of tropical IO plays the most important role and the warming in the South IO is important for monsoon prediction prior to the full development of monsoon. More specifically, the atmospheric response to the basin wide warming is very similar with that to tropical IO warming, corresponding to significantly less precipitation in the SAM region and weaker summer monsoon circulation over South Asia and Southeast Asia. The influence of the North IO warming on SAM is opposite to that of the South IO warming. However, the linear superposition of the responses caused by North IO warming and South IO warming suggests a high similarity with the responses caused by basin wide IO warming. Besides, the North IO warming in spring seems to favor an early onset or a large persistence of the SAM.