Intensified Impact of East Indian Ocean SST Anomaly on Tropical Cyclone Genesis Frequency over the Western North Pacific

Abstract

recent finding is the significant impact of the sea surface temperature anomaly (SSTA) over the east Indian Ocean (EIO) on the genesis frequency of tropical cyclones (TCs) over the western North Pacific (WNP). In this study it is shown that such an impact is significant only after the late 1970s. The results based on both data analysis and numerical model experiments demonstrate that prior to the late 1970s the EIO SSTA is positively correlated with the equatorial central Pacific SSTA and the latter produces an opposite atmospheric circulation response over the WNP to the former. As a result, the impact of the EIO SSTA on the TC genesis over the WNP is largely suppressed by the latter. After the late 1970s, the area coverage of the EIO SSTA is expanding. This considerably enhances the large-scale circulation response over the WNP to the EIO SSTA and significantly intensifies the impact of the EIO SSTA on TC genesis frequency over the WNP. The results from this study have great implications for seasonal prediction of TC activity over the WNP.