Investigating the Effects of Super Typhoon HAGIBIS in the Northwest Pacific Ocean Using Multiple Observational Data

Abstract

Various multi-source observational platforms have enabled the exploration of ocean dynamics in the Northwest Pacific Ocean (NPO). This study investigated daily oceanic variables in response to the combined effect of the 2019 super typhoon HAGIBIS and the Kuroshio current meander (KCM), which has caused economic, ecological, and climatic changes in the NPO since August 2017. During HAGIBIS, the six-hourly wind speed data estimated a wind stress power (Pw) which strengthened around the right and left semicircles of the typhoon, and an Ekman pumping velocity (EPV) which intensified at the center of the typhoon track. As a result, firstly, the sea temperature (ST) decreased along a boundary with a high EPV and a strong cyclonic eddy area, and the mixed layer depth (MLD) was shallow. Secondly, a low sea salinity (SS) concentration showed another area where heavy rain fell on the left side of the typhoon track. Phytoplankton bloom (PB) occurred with a large concentration of chlorophyll a (0.641 mg/m3) over a wide extent (56,615 km2; above 0.5 mg/m3) after one day of HAGIBIS. An analysis of a favorable environment of the PB’s growth determined the cause of the PB, and a shift of the subsurface chlorophyll maximum layer (SCML; above 0.7 mg/m3) was estimated by comprehensive impact analysis. This study may contribute to understanding different individually-estimated physical and biological mechanisms and predicting the recurrence of ocean anomalies.