Analysis of the effects on sea surface temperature and ocean color environment by typhoon Haitang (2005) based on remote sensing in Taiwan Strait

A typhoon (as well as a hurricane or tropical storm) is one of the largest air-sea interaction processes on the synoptic scale, which can greatly enhance the air-sea exchange of material and energy within a short time; meanwhile, a typhoon can significantly alter the water structure, seabed topography and geomorphology, and particle transport and deposition, as well as biogeochemical processes in the affected areas. Satellite remote sensing is the main approach to study the impact of typhoon on the sea surface temperature(SST) and the ocean color environment at present. The Taiwan Strait plays an important role in water and sediment exchange between the East China Sea and the South China Sea. This paper uses the data of the MODIS satellites to analyses the effects of Haitang(2005) on the SST, sea surface chlorophyll-a concentration(Chl-a) and total suspended matter(TSM) in the Taiwan Strait over different periods. During the typhoon-active period, the concentration of TSM significantly increased. The SST for the typhoon-active period was lower than that both the pre- and post- the typhoon periods. During the typhoon, Chl-a concentration increased. After the typhoon, the Chl-a concentration decreased, but still higher than before the typhoon. The Chl-a concentration near the Minjiang Estuary during the typhoon was slightly lower than that before the typhoon and after the typhoon. During the typhoon, the strong cyclonic wind-stress of the typhoon enhanced heat exchange between the water and the atmosphere, and a large amount of rainfall and run-off significantly decreased the SST. During the typhoon, the increased sediment discharged into the strait by rivers, and the re-suspension of seafloor sediment, increased the concentration of TSM in the coastal waters. Seawater with relatively high sediment concentration was transported to the middle of the strait after being carried by wind-induced flows. During the typhoon, in the waters near the typhoon's path, Chl-a concentration increased. After the typhoon, Chl-a concentration near the Minjiang estuary dramatically increased than before the typhoon. Nutrient-rich bottom water stirred by the typhoon promoted an outbreak of aquatic organisms. The increase of Chl-a concentration has a certain delay because the growth of organisms takes time.