Impacts of tropical ocean warming on East Asian summer climate

The impacts of eastern Pacific (EP) and Indian Ocean (IO) warming after the late 1970s on the East Asian climate in July and August were investigated, to understand the distinct impacts of the abovementioned warming on differences in sub-seasonal characteristics. The EP warming induced a strong Pacific-Japan (PJ)-like (tropics-related meridional) pattern during July, but the IO warming preferred a Eurasian (EU)-like wave (extratropics-related zonal) pattern during August. The former is weaker in August and the latter in July. Additionally, the results of perpetual July and August model experiments revealed that these distinct atmospheric responses to the EP and IO warming during July and August, respectively, were caused by different mean thermal states. The difference in the mean thermal states was mainly derived from (1) a warmer ocean and cooler continent in August than in July and (2) a warmer tropics and cooler extratropics in July than in August.