Research On The Relationship Between Mesoscale Eddy And Chlorophyll Distribution Based On Remote Sensing Data

Mesoscale eddy in the ocean is important mesoscale phenomenon,its time scale in a few days to a few months between,space scale between tens to hundreds of kilometers.it can provide huge kinetic energy,the waters around the nutrient composition such as carrying to the sea,in the direction of propagation of sea surface height,sea surface temperatures,sea surface salinity,spatial and temporal variations of the oceanic elements such as chlorophyll concentration to make a certain contribution.During the life cycle of eddy,mesoscale eddy will carry the lower cold water to the sea surface,and the nutrients in the lower cold water will also bring to the sea surface,promoting the growth,development and reproduction of zooplankton in the sea surface,and realizing the redistribution of nutrients at different levels through this process.The process that the mesoscale vortex on the ocean dynamic process,the energy distribution and make important contributions to the material transport through the study of physical properties and eddy current eddy feedback effects on the Marine biological process,can contribute to the dynamic early warning and forecasting of Marine sea condition,the variation function and the sustainable development of the Marine ecological environment and related research.In this paper,we identified and tracked the mesoscale eddies in the Kuroshio extension region between 2020 and 2021 using AVISO mesoscale eddies.The temporal and spatial distribution characteristics of the mesoscale eddies and the Chl-a in the Kuroshio Extension from 2020 to2021 were studied,and the variation of the concentration anomaly of Chl-a in the Kuroshio Extension mesoscale eddies was analyzed by normalization.The results show that:A total of 8,526 cyclones and 7,716 anticyclones were detected in the study area.The spatial distribution of mesoscale eddies in this region is as follows: the average eddy kinetic energy distribution of the Kuroshio Extension is zonal in zonal direction,and the high value of eddy kinetic energy is located on the main axis of the Kuroshio Extension in east-west direction,mainly distributed near 36°N.The number of cyclones is larger than anticyclones,and there are more long-period cyclones,while the period of anticyclones is generally shorter.The spatial and temporal variation features are as follows: there are seasonal differences in the number,amplitude and effective radius of air vortices in summer,autumn,winter and spring.The number of vortices extracted in spring is relatively large,but the amplitude of vortices in spring is generally small and the effective radius is relatively small.The number of anticyclones is relatively large in spring and summer,and the average effective radius of the anticyclones in spring is relatively small,but the average amplitude in summer is relatively small,and the amplitude in spring is much larger than that in summer.The annual average distribution of chlorophyll distribution in the study area presents a zonal pattern,gradually decreasing from high latitude to low latitude,and presents a certain degree of tilt.At the same latitude,the chlorophyll concentration in the west is higher than that in the east,and there is a high value region of chlorophyll concentration in the near shore.The variance of Chl-a in the study area has nothing to do with latitude,and its overall size is positive.On the time scale,The value of Chl-a showed a decreasing trend in May and continued to the end of September,and then gradually increased until April.The mean value of Chl-a in this region was significantly affected by seasons.Through periodic normalization,the amplitude variation of long-period cyclone and anticyclone in kuroshio extension area is basically the same,and the cyclonic amplitude variation shows a trend of increasing first and then decreasing.After that,with the extinction of eddy,the eddy amplitude decreases continuously,but the average amplitude reached at the final extinction is still larger than the initial stage.The anomalous distribution of Chl-a in the vortex obtained by radius normalization shows that the level of Chl-a in the air vortex increases as a whole,while that in the anticyclone decreases as a whole.The activity of air vortex is particularly intense in spring,which can also be compared to show that,compared with the cyclone,the anticyclone is less affected by the season,and the degree of air vortex is greater,and the degree of CHL-A anomaly in the cyclone caused by this is also relatively greater.In addition,the results show that,unlike the long-period eddy,the Chl-a anomaly in the shortperiod eddy is almost concentrated in the eddy center,which cannot explain the dipole variation caused by eddy stirring.