Construction Of Ideal Mesoscale Eddy Model Based On ROMS And The Influencing Factors Of Non-externally Forced Westward Movement Of Mesoscale Eddies

The ocean mesoscale eddies is an important component of dynamic oceanography.Marine mesoscale eddies play an important role in the transport of ocean materials and energy,the regulation of global climate change,and the distribution of marine natural resources.For the oceanic problem of mesoscale eddies,observations and numerical models are generally used.In recent years,altimeter data and Argo buoy data have been accumulated,and numerical models have also developed rapidly.There are also certain solutions to the problems related to mesoscale eddies.However,there is no unified conclusion about the westward movement of mesoscale eddies.Therefore,the main purpose of this paper is to use the ROMS model to construct an ideal mesoscale eddy structure,and then perform some mesoscale eddy ideal experiments to explore the factors affecting the westward movement of mesoscale eddies.This paper first uses the ROMS model to construct the ideal three-dimensional structure of mesoscale eddies.There are two methods to do this,one is to create a mesoscale eddy driven by a typhoon-like wind field on the surface of the ocean,and the other is to use an eddy normalized three-dimensional formula to construct the ideal mesoscale eddy.After the ideal mesoscale eddy is constructed,it is input into the ROMS model in the form of the initial field.Some characteristic parameters of the eddy,such as eddy intensity,f0 parameter,beta parameter,and background field temperature,are set in the model.A series of comparative experiments for mesoscale eddies are conducted to explore the factors affecting the eddy westward movement.These experiments were done without background flow and without wind forcing.Experiments one to six are independent experiments,and each experiment has several comparative small experiments.In Experiment one on the f-plane and P-plane,the movements of mesoscale eddies show that,first of all,a mesoscale eddy can exist in the f-plane at a constant level and decay more slowly than the eta kinetic energy in the ?-plane,and the mesoscale eddy in the f plane has no apparent westward movement.Second,in the beta plane,either a warm eddy or cold eddy has obvious westward motion,and the warm eddy moves westward and the cold one moves northwestward.The only difference between the f-plane and the ?-plane in experiment one is that there is a Coriolis force parameter gradient in the ?-plane but there is no in the f-plane.So it can be said that in the absence of other external factors(such as currents,wind fields,etc.),the mesoscale eddy with the presence of a Coriolis force gradient will move westward.In Experiment two,mesoscale eddies were tested in actual latitude and longitude regions.It was found that the mesoscale eddies had a significant westward motion and the warm eddies deflected toward the equator and the cold ones deflected polarward.This is consistent with the mesoscale eddies moving in the ? plane.Experiment three to Experiment six are performed under the P plane.Experiments three to six explored the effects of beta parameters,fO parameters,eddy intensity,and background field temperature on the mesoscale eddy westward motion,respectively.In Experiment three,the effect of the beta parameter on mesoscale eddy movements was examined.In the model,the mesoscale eddy is the same,only the beta parameter values are set differently and the other settings are the same.It was found that the westward movement velocity of mesoscale eddies linearly increases with the beta parameter increasing.In the experiment four,the comparison experiment of the influence of the f0 parameter on the mesoscale eddy motion shows that a series of mesoscale eddies with the same size and similar average eddy kinetic energy are constructed under different f0 parameter values,and only the f0 parameter values are set differently and the other settings are the same,the velocity of the mesoscale eddy westward movement is very different,and with the increase of the f0 parameter,the westward movement velocity of mesoscale eddies linearly increases.In experiment five,the comparative experiments on the effect of mesoscale eddy intensity on mesoscale eddy movements demonstrated that mesoscale eddy of the same size but with different average surface eddy kinetic energy and the other settings of the model are the same,the westward movement velocity of the mesoscale eddy is very different,and the higher the average eddy energy of the mesoscale eddy,the greater the westward movement velocity of the mesoscale eddy,and the greater the southward movement velocity of the warm eddy and the northward movement velocity of the cold eddy.In Experiment six,the comparative experiments on the effect of background temperature on mesoscale eddy movements showed that in models where only the background temperature field is set differently,and other settings are the same,the westward movement velocity is very different,the lower the background temperature field is set,the smaller the westward movement speed of the mesoscale eddy with the same size and the average eddy kinetic energy formed under this background temperature field,and the smaller the southward movement velocity of the warm eddy and the northward movement velocity of the cold eddy.In this paper,we first constructed the ideal mesoscale eddy structure in the ROMS model,and then performed a series of ideal experiments on the mesoscale eddy movement.The results demonstrated that in the absence of other external factors(such as currents,wind fields,etc.),only In the presence of a Coriolis force gradient,the mesoscale eddy moves westward,and its westward propagation velocity increases with the increase of the beta parameter and eddy intensity,and decreases with increasing fO parameter.As the overall temperature of the background field increases,it increases.