Composite of Typhoon-Induced Sea Surface Temperature and Chlorophyll-a Responses in the South China Sea

Abstract

Sixteen years of data on typhoons in the South China Sea (SCS) are used to investigate their impacts on sea surface temperature (SST) and chlorophyll-a (Chl-a). The time series of SST and Chl-a before and after typhoons are composited for all typhoon locations to assess their responses. Decreases in SST and increases in Chl-a occur after 73% and 70% of the typhoons, respectively, with overall averaged changes equal to −0.42 ± 0.015°C and 0.056 ± 0.003 log10 mg/m3, respectively. The largest responses are found near the typhoon center, and the extent of changes in these parameters decreases linearly with distance. The SST responds rapidly, starting to drop 2 days ahead of the typhoon passage and continuing to drop until 2 days after its passage. On the other hand, the Chl-a increases after the typhoon passage, remaining high for 5 days before beginning to return to the initial conditions. Large (weak) changes are associated with typhoons that have high (low) wind speeds and slow (fast) translation speeds. This is especially true for SST, whereas some typhoons with slow translation speeds are characterized by increases in Chl-a, mostly occurring near the coast. The largest SST and Chl-a changes induced by a single typhoon are found in the upwelling region off Vietnam. The study offers a comprehensive quantitative analysis that describes the general pattern of SST and Chl-a responses to typhoons in the SCS.