Remote Sensing Monitoring Of Ulva Prolifera Blooms In The Southern Yellow Sea From 2008 To 2021

In July 2021,the largest green tide occurred in the Qingdao sea area in history,which was also the green tide in the Southern Yellow Sea area for 14 consecutive years,causing huge economic losses to coastal cities and serious harm to the Marine ecological environment.In view of the characteristics of rapid outbreak time and wide distribution of green tide,it is particularly important to use remote sensing to monitor it.In this study,MODIS,ESRL,GPM,RSS data and GIS technology were used to compare the detection ability of five traditional vegetation indices for green tide in the Southern Yellow Sea from 2008 to 2021,and the influence of various environmental driving factors of the green tide outbreak was explored,and corresponding prevention strategies was proposed.It provides scientific reference to the monitoring and control of green tide in the Southern Yellow Sea.The main results are as follows:(1)Based on MODIS data,the detection ability of five traditional vegetation indices(NDVI,EVI,SAVI,DVI and ARVI)was analyzed.The results showed that the detection ability of Normalized Difference Vegetation Index(NDVI)was the best,which could be used as the preferred method to extract the remote sensing information on green tide in this paper.(2)Using MODIS data from May to August of 2008 to 2021,the information about green tide in the Southern Yellow Sea was extracted.The research shows that: The areal variation characteristics of green tide in the Southern Yellow Sea from 2008 to 2021 are as follows: green tide appeared from May to August every year and the duration of each year was different,with the longest duration in 2019.The outbreak of green tide experienced complete emergence,development,outbreak,recession and extinction stages every year,and the change of the area covered by the green tide showed a single-peak law.The coverage area and distribution area of green tide varied greatly and did not have synchronicity.The spatial variation characteristics of green tide in the Southern Yellow Sea were as follows: the area first monitored was concentrated on the northern part of Yancheng,Jiangsu province(33°—35°N,121°—122°E),and then gradually differentiated and developed in the northern part of Yancheng.Influenced by the southeast monsoon in the study area,the green tide gradually drifted northward and developed to the coastal waters of Qingdao.Subsequently,it continued to drift into the northeast due to the geographical isolation from Shandong Peninsula,and finally accumulated and gradually disappeared on the southern coast of Shandong Peninsula.The scale of the influence of green tide showed a trend of increasing fluctuation.The distribution range of green tide expanded on offshore to offshore,and the affected coastline extended to the southern coast of Shandong Peninsula to both sides.(3)Based on ESRL SST,GPM precipitation and RSS wind field data,the results showed that SST and precipitation in the Southern Yellow Sea were significantly correlated with the outbreak of green tide,and the southeast monsoon in the Southern Yellow Sea was an important driving force of the northward drift of green tide.According to the growth characteristics of the green tide in different periods,while reducing the eutrophication of seawater from the root,measures such as monitoring in advance,timely fishing,exploitation and utilization of the salvage of green tide can be taken to prevent and control the green tide and reduce the disaster caused by the green tide.