Attribution of the summer warming since 1970s in Indian Ocean Basin to the inter-decadal change in the seasonal timing of El Nio decay phase

摘要

This paper reports that, on top of the general warming trend in the Indian Ocean Basin (IOB) SST in the past 140years, there exists an additional multidecadal-scale warming in the period from late 1940s to early 2000s, and this warming in IOB is particularly stronger in summer than in other seasons. Our analysis indicates that, the seasonal timing of the decay phase of El Nio events during this period has been delayed from spring to early summer since 1970s, while the seasonal timing of La Nia decay phase remains in spring season. The direct effect of the later decay of El Nio events is the lengthening of the delayed warming effect of El Nio on IOB SST into summer, attributing to the stronger IOB warming in summer from the late 1940s to the early 2000s.