The Mesoscale Eddies’ Detection Method Research From Altimeter And Numerical Model Data

Mesoscale eddies are ocean vortexes whose spatial scale is tens to hundreds kilometers and time scale is several days to several months. They contain large kinetic energy and play important roles in the whole ocean circulation. Due to the altimeter has good temporal resolution, spatial coverage, quasi synchronous and continuous time, more and more people begin using altimeter to detect mesoscale eddies in the ocean. Similarly, numerical models also have the advantages of perfect physical process, stable model framework and numerical method as well as adapting to the competed area, more and more people begin using numerical model to simulate mesoscale eddies.The paper combines provided by French space agency AVISO data center and merged many satellite altimeter’s MSLA grid data’ SLA data and SSH data as well as HYCOM model data to detect mesoscale eddies. The selected research area is 103°-121°E,0°-23°N.Firstly, the paper introduces several kinds of mesoscale eddies detection methods, such as SSHA method, O-W parameter method, Winding-Angel method and Vector geometry method. Secondly, based on altimeter data the paper begin to use SSHA method and vector geometry method detecting mesoscale eddies. Then the paper shows the detection results and analysis mesoscale eddies’ feature from eddies’ space distribution, number statistics, existing period and moving trajectory. The result shows that mesoscale eddies are mainly distributed in the northeastern South China Sea and the eastern area of Vietnam. The distribution patterns of warm eddy and cold eddy are similar. Except January and June, in different months the number of mesoscale eddies vary little. Seasonal variation of mesoscale eddies is not obvious.There are more warm eddies in summer and more cold eddies in winter. The existing period of mesoscale eddies mostly concentrate in 30-60 days. Obviously, warm eddies’ existing period is longer than cold eddies.Finally, based on HYCOM data, the paper uses vector geometry method to detect mesoscale eddies in the South China Sea in January and February,2012.Then the paper shows the detection results and analysis mesoscale eddies’ feature from eddies’ space distribution,number statistics, existing period and moving trajectory. The result shows that during the period, we totally detect 11 mesoscale eddies which contains 6 cold eddies and 5 warm eddies.Compared with eddy move trajectories obtained by altimeter data, the eddy move trajectories obtained by HYCOM data are more concentrate. This may related with mesoscale eddies’ slow moving speed and the little change of eddy center’ location.