The Influence Of Different Weather Circulation On The Surface Chlorophyll Concentration Of The South China Sea Was Studied Based On Multi-source Satellite Remote Sensing

Phytoplankton plays an important role in the atmosphere-ocean carbon cycle due to its carbon fixation.As one of the representative components of phytoplankton,chlorophyll-a can not only indicate marine phytoplankton abundance and primary productivity,but also indicate the impact of climate change on the marine environment.In the past,studies on chlorophyll-a and meteorological conditions were mostly concentrated on the seasonal-interannual-decadal scales,and there were few studies on weather scales(excluding typhoons)and diurnal changes.Therefore,this article uses high spatio-temporal resolution multi-satellite data or ocean reanalysis data to systematically study the impact of different atmospheric circulation and extreme weather events on the surface chlorophyll-a concentration through on the weather scale and diurnal variation in South China Sea.The general conclusions are as follows:1)Based on the T-mode principal component analysis method,we divided the 500 h Pa atmospheric circulation in the South China Sea in summer of 2015–2018 into four types.It is found that four types of weather patterns are closely related to the Northwest Pacific Subhigh.Chlorophyll-a and sea surface temperature show significant differences in spatial distribution and diurnal variation under different weather types.These differences are jointly modulated by monsoon circulation,local mesoscale processes in the ocean,and changes in hydrometeorological conditions such as rainfall,wind,and sunlight under different weather patterns.2)Super Typhoon Mangkhut(2018)not only caused a significant increase in the chlorophyll-a concentration and daily growth rate near its path through the role of “wind pump”,but also indirectly caused changes in the chlorophyll-a concentration by causing changes in the horizontal flow of the Beibu Gulf.It even changed the chlorophyll-a concentration in southern Vietnam far from the path of the typhoon through the coupling effect with the monsoon.3)When there is a low-level jet in the Beibu Gulf in summer,stronger southwesterly winds appear on the sea surface,and changes in light and precipitation,resulting in changes in chlorophyll-a and sea surface temperature.Especially in the nearshore,the peak value and diurnal amplitude of chlorophyll a are larger on low-level jet days.In general,on the weather system,the impact of weather conditions on local hydrometeorological and marine biophysical environment changes cannot be ignored.This will have important scientific implications for understanding the formation mechanism of the marine biophysical environment of the South China Sea and for monitoring,forecasting and evaluation.