Mesoscale Eddy Information Extraction And Movement Law In The South China Sea

Mesoscale eddy is an important mesoscale marine phenomenon,which exists widely in oceans all over the world.With the rapid development of satellite altimetry technology,altimeter products with high spatio-temporal resolution have injected new vitality into the study of mesoscale eddies.In recent years,the field of marine environment monitoring and safeguarding has received increasing attention,and mesoscale vortices play an important role in the safety of the marine environment.Therefore,in this paper,the South China Sea is used as an experimental area to study the extraction of mesoscale vortex information and their characteristics.First of all,the background and significance of the research on the extraction of mesoscale vortex information in the South China Sea and the analysis of its movement laws are cited.The current status of domestic and foreign research in related fields is listed.The altimeter principle is introduced.The reanalysis data is introduced afterwards,and two sources of data are finally given.Secondly,satellite altimeter data from January 1993 to December 2018 were used to identify and track mesoscale vortices in the South China Sea.In view of the large calculation volume of the classical thresholdless contour method and the inaccurate definition of the edges of the mesoscale vortex,this paper optimizes the search from local extreme points and judges the relationship between contours.Measure the mesoscale vortex while calculating its parameters-radius,amplitude,velocity,etc.In order to find the complete mesoscale vortex trajectory,it is necessary to track discrete mesoscale vortices,introduce similarity based on the minimum distance method,and add a limit of amplitude to ensure the accuracy of the tracking.Then using the reanalysis data,an anticyclone and a cyclone were selected to study their vertical temperature-salt structure.Thirdly,based on the 26-year extraction results,statistical analysis was performed on the number,radius,amplitude,life cycle,growth and extinction sites,kinetic energy,and vorticity of mesoscale vortices in the South China Sea.It is found that the average annual lifespan(amplitude)of cyclone and anticyclone in the South China Sea is 41 mesoscale vortices,which are 53 days(5.72cm)and 55 days(5.20cm).Skewed normal distribution.Later,the movement characteristics of mesoscale vortices were studied,and the average moving speed was 5.19cm/s.Most vortices did not move more than 300 km.Nearly half of the mesoscale eddies in the whole sea area have nonlinear characteristics.These are good for the following predicted trajectories bedding.At present,there are few studies on the prediction of the trajectory of the mesoscale vortex in the South China Sea.Due to the strong nonlinearity of the mesoscale vortex,it is difficult to choose the physical factors that affect its movement.Therefore,this paper uses a back propagation neural network as the trajectory prediction model.A single feature trajectory is used as input,and the forecast window is 3 days.Using 1993-2013 South China Sea mesoscale vortex trajectories as the training set and 2014-2018 trajectories as the verification set,selecting appropriate evaluation indicators,the results show that the model has achieved good results in prediction.