The Impact Of Tropical Cyclone Translation Speed And Intensity On Phytoplankton Chlorophyll-a Concentration In The Northern South China Sea

The South China Sea(SCS) has a particularly prominent strategic position and economic meaning to our country. Exploring the effects of tropical cyclone(TC) on primary productivity and fishery resources in the ocean has important significance in the development and utilization of the SCS. In this study, we adopted the remote sensing data, analyzed the translation speeds and intensities of 21 TCs which invaded SCS during 2002~2010 summer(June to September), discussed the change of chlorophyll a concentration pre- and post-TC. Noguri,2002 and Hagupit,2008 were studied during their passing through the northern SCS. Noguri originated at its study area(18.5°N~20.5°N, 112°E~114°E) as a tropical depression, and moved out after 48 hours on its slow translation speed(1.4m·s-1), Noguri was so weak(10m·s-1) during that period; Hagupit appeared as a high intensity(≥50m·s-1) and fast moving(8m·s-1) TC in its study area(19.5°N~21.5°N, 115.5°E~117.5°E). By analyzing the intensities and translation speeds of these two cases with tremendous difference, it was found their distinct influence on the upper ocean. These three variables, intensity, translation speed and chlorophyll a concentration growth rate have a complex relationship. By doing the partial correlation analysis, to estimate the other two variables when the intensity or translation speed was under control.This paper studied the responses of chlorophyll a concentration under TC, based on the similar oceanic and atmospheric background. It is practical to find out the relationship between TC translation speed, intensity and chlorophyll a concentration growth rate by establishing the binary linear regression model. Strong wind affects a certain area for a long time can make the surface pressure much lower, the strong upwelling will bring the deeper cold water rich in nutrient up to the surface, thus the chlorophyll a concentration can be increased. It was found that, the regression coefficient of intensity is in the same order of magnitude with the regression coefficient of translation speed, shows that the effects bring by translation speed and intensity are both important.