Satellite based observation of enhancement of Chlorophyll-A concentration by typhoon — NARI

Abstract

Several recent studies have demonstrated the enhancement of chlorophyll a (Chl-a) concentrations on the surface of the ocean, induced by typhoons. The present study investigates the Chl-a concentrations in the South China Sea (SCS) for 2013 after the passage of typhoon NARI which was part of the 2013 Pacific typhoon season. Remotely-sensed wind speed, sea surface temperature (SST) and chlorophyll data are used to understand the physical and biological response of the ocean to this typhoon. Sea surface cooling (SSC) is observed in the satellite data with the temperature decreasing to about 2–4 °c. This is attributed to the strong winds that are associated with the typhoon event. Further, an assessment of the Chlorophyll a Aqua MODIS data shows an increase in the Chl-a concentration to about 0.8 mg m−3, 2–6 days after the passage of NARI. It can be suggested that a sub-surface upwelling caused by the passage of the typhoon, transported nutrients to the euphotic zone and caused the Chl-a bloom. This study therefore provides a relevant insight on the effect of typhoons on the marine ecosystem, especially related to Chlorophyll-a estimation and subsequently to primary production studies.