Relationships between Springtime Sea Surface Temperatures in Different Indian Ocean Domains and Various Asian Monsoons from Late Spring to the Following Summer

We investigate the relative importance of spring sea surface temperatures (SSTs) in different Indian Ocean (IO) domains, especially the northern and southern IO, for the development and intensity of the Asian summer monsoon. By performing unsupervised neural network analysis, the self-organizing map, we extract distinct patterns of springtime IO SST. The results show that the uniform warming (cooling) of the southern IO plays a crucial role in the warming (cooling) of both the basin-wide IO and tropical IO. The southern IO thus well represents the associations of basin-wide IO and tropical IO with the Asian summer monsoon, and is instrumental in the relationship between the IO and summer monsoon. A warming in the southern IO is closely related to the weakening of large-scale meridional monsoon circulation in May and summer (June–August), including suppression of the South Asian monsoon development in May and the East Asian monsoon in summer. On the other hand, a warming in the northern IO appears to be associated with an earlier South Asian monsoon onset and a stronger East Asian monsoon. In summer, the connection of the springtime IO SST with the South Asian monsoon weakens, but that with the East Asian monsoon strengthens. Finally, a robust negative correlation is found between the warming of various IO domains and the development and intensity of the Southeast Asian monsoon.