Respective and combined impacts of regional SST anomalies on tropical cyclogenesis in different sectors of the western North Pacific

Tropical cyclone activity over the western North Pacific (WNP) is subjected to impacts of sea surface temperature (SST) anomalies in the three tropical oceans. In this talk, the interannual variations in the tropical cyclone (TC) over the WNP and the influences of regional SST anomalies are documented by separating the WNP into four quadrants considering SST-induced non-uniform environmental changes. It will be shown that the TC variations in the northwest and southeast quadrants are related to both equatorial central-eastern Pacific (EPO) and tropical Indian Ocean (TIO) SST anomalies. The TC variation in the northeast quadrant is mainly related to tropical North Atlantic Ocean (TNA) SST anomalies. The main environmental variables differ for the TC variations in the four quadrants. Low-level (850-hPa) vorticity is important for the TC variations in the northwest, southwest and southeast quadrants. Mid-level (700-hPa) humidity contributes to the TC variations in the northwest, northeast and southeast quadrants. The vertical shear has a supplementary contribution to the TC variation in the southeast quadrant. The potential intensity negatively affects the TC variations in the southwest and southeast quadrants. The remote SST anomalies modulate different environmental variables over the WNP. The TIO SST influence is manifested in the low-level vorticity and vertical motion. The TNA SST impact occurs through the low-level vorticity change. The EPO SST effect occurs via changing the low-level vorticity and vertical motion as well as the mid-level moisture and vertical shear. The environmental variables experience more prominent changes when SST anomalies coexist in two remote regions. Numerical experiments confirm the EPO and TIO SST anomaly impacts on the environmental conditions affecting the WNP TC variations.