Studying Upper Ocean Of South China Sea Responses To Typhoon Based On Remote-sensing Data And Reanalysis Data

The South China Sea(SCS)is the largest marginal sea in China.It possesses superior strategic geographical location and abundant sea resources.Meanwhile,it's an important traffic fortress at sea.However,the SCS is a place where nature disasters happened frequently,like storm surge and typhoon,etc.Not only do typhoons have effects on marine ecology and hydrodynamic environment,but on offshore fishery,marine transport,marine engineering activities too,and so on.Therefore,it is significant to do research about features of SCS upper ocean responses to typhoon when they come.This paper mainly took advantage of remote sensing and HYCOM reanalysis data to study upper ocean of SCS responses to typhoon.Firstly,it paid much attention to 201409 super typhoon “Rammasun”,and analyzed the response features of marine ecology and hydrodynamic environment in the SCS systemically.Also,the paper adopted EOF to analyze and study the temporal and spatial features on the SST,MLD and rainfall after super typhoon “Rammasun” in SCS.Secondly,the changeable features of sea surface temperature(SST),mixing layer depth(MLD)and chlorophyll concentration(Chl)in the paper were deeply analyzed mainly based on typhoons sample data of recent decade and combined remote sensing data with HYCOM reanalysis data.The result showed that super typhoon “Rammasun” induced strong entrainment and upwelling and strengthened seasonal upwelling at same time.After the typhoon,the SST of SCS decreased rapidly,and the maximum degree of decrease close to 2?.We also found that the SST will turn to normal level slowly after half a month.Sea surface temperature reduction showed “right bias” while spatial of rainfall displayed “left bias” phenomenon compared to typhoon path.What's more,super typhoon brought rainfall to the SCS.After the typhoon,the suspended sediment concentration(SSC)and the chlorophyll concentration rised 51.4% and 28% in the northwestern South China Sea,respectively.For the latter,the maximum concentration delayed 3 days,and primary productivity increased 34%.Besides,upper water column mixed violently and the depth of mixing layer increased close to 10.4m.In recent 10 years,all kinds of cyclones and typhoon through the SCS were up to 94 times.There were 49 times over typhoon level,which account for 52%.One to two times of super typhoon would happened per year on average.In study area,average SST was 29.05? before the typhoon and average SST was 28.22?,wih average reduction of 2.84%;average MLD was 19.56 m before the typhoon and average MLD was 28.31 m,wih average growth of 58.57%;average Chl concentration was 0.29 m/L before the typhoon and average Chl concentration was 0.43 m/L,wih average growth of 60.11%.The maximum cooling of SST and maximum chlorophyll concentration had a general delay effect,however,maximum MLD had good synchronization with typhoon.