| Tropical cyclone is closely related to the upper ocean.It is an important influence system for the response of the upper ocean to the atmosphere.The ocean mesoscale eddies are kind of common natural phenomenon in the ocean.They bear the responsibility of transporting heat,salt and nutrients for large-scale systems.They affect the circulation structure of the sea area,the distribution of large water masses,and marine life as well.Therefore,they are of great significance to study the impact of tropical cyclones on mesoscale eddies.In this paper,satellite remote sensing data and ROMS-coupled model data are used to analyze the types,efficiencies and mechanisms of cyclone eddies' response to tropical cyclones.Firstly,three types of response methods are defined.Tropical cyclones can promote cyclonic eddies generated below the path;tropical cyclones can strengthen the existing cyclonic eddies intensity below the path;tropical cyclones can weaken the cyclonic eddies around the path..The temperature response of the cyclonic eddies to tropical cyclones generated or enhanced by the effect of tropical cyclones below the path is characterized by a decrease in the sea surface temperature caused by the tropical cyclone in the general ocean background field,and the presence of the cyclone eddies reduces the sea surface temperature and increase the amplitude of temperature reduction in the vortex region,which keeps their larger continuous cooling.Later,through statistics on the effects of tropical cyclones over the study area(105-130°E,5-30°N)from 2000 to 2015 on the cyclonic eddies,it was concluded that 86%of the tropical cyclones that passed through the study area in 16 years passed gas.In the eddies,only less than 13%of the tropical cyclones caused a significant impact on the cyclone eddies under the path,reflecting the inefficiency of tropical cyclones affecting the cyclonic eddies below the path.A total of 41 cyclonic eddies responded markedly to their 35 tropical cyclones,of which 7 cyclones were generated as a result of tropical cyclones and 34 were strengthened.In addition,the statistics found that in addition to strengthening the cyclonic eddies below the path,the tropical cyclone weakened the cyclonic eddies around the path,and a total of 12 paths around the cyclone vortex were weakened by tropical cyclones.Then,the effects of the three parameters of tropical cyclones on the cyclonic eddies generated or enhanced under 41 paths were analyzed by linear regression.It was found that the correlation between forced time and cyclone vortex parameters was the best,because the forced time combined not only with tropical cyclones.The wind speed intensity and speed of movement also take into consideration its role.However,the relationship between the area change of the cyclonic eddies and the parameters of the tropical cyclone is not ideal,reflecting that the effect of the area of the cyclonic eddies on the vortex intensity is not obvious.Finally,the variables affecting the vortex heat balance of the cyclone were analyzed and discussed using the ROMS coupled model.After a tropical cyclone passes over a cyclonic eddies,it will cause the cyclonic eddies to lose a lot of heat,and the state of heat loss can last for a long time.According to the analysis of the thermal budget of the upper cyclonic eddies,the causes of the cyclonic vortex cooling and heat loss are:temperature level advection,temperature vertical convection,and air-sea heat flux.The vertical temperature convection item showed a downward trend on the day after the tropical cyclone passed,and its value was less than zero.It dropped to an extreme value on the day after the tropical cyclone passed or lag one day,and then quickly recovered(in 2012,the case occurred on the day of tropical cyclone transit.The vertical convection items are weakened,leading to an upward trend on the day.)The temperature advection of the cyclone vortices showed an upward trend on the first day of tropical cyclone transit,and was greater than zero,and the day afterwards began to decrease.The net heat flux of the sea surface of the cyclonic eddies showed a decreasing trend on the day after the tropical cyclone passed,and it was less than zero.After transiting to the extreme day or lagging one day,the net heat flux gradually recovered.In the absence of the effect of tropical cyclones,the net heat flux of air-sea gas occupies the major factor affecting the cyclone vortex heat budget.When there is a tropical cyclone over the cyclonic eddies,the vertical convection project dominates,and the temperature advection term and the net heat flux of the air and sea are followed.However,when the subsurface of the cyclone vortex rises and the upwelling is weakened,the effect of the temperature advection term is equivalent to that of the vertical convection term.The proportion of changes in the three items and their contribution also reflects that the responses of the cyclonic vortices to tropical cyclones passing over them mainly through three mechanisms.The first is the direct exchange of tropical air cyclones with the cyclonic eddies,which has little effect on the transit of tropical cyclones.In addition,the heat redistribution caused by the internal flow of the ocean caused by the transit of tropical cyclones is reflected by the divergence of horizontal currents within the vortex,and the Ekman upwelling caused by tropical cyclones.The loss contribution is the largest of the three.However,when the divergence of the cyclone vortex surface is strong,the sink flow caused by the divergence flow will weaken the Ekman ascending flow.At this time,the contribution of the divergent flow and vertical updraft to the cyclonic eddy heat loss is equivalent. |
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