Diagnostic Analysis Of The Formation And Movement Of Tropical Cyclones In High-Resolution Numerical Simulation

There are about 9 tropical cyclones on average making landfall in China every year,which causes about 37 billion yuan in financial loss.With the development of computers and numerical models,researches on the formation and movement of tropical cyclones focus much more on fine structure of tropical cyclones.Some problems are found in this study when researching the genesis and movement of tropical cyclones with a high-resolution model.This article provides mechanism analyses and suggestions.The main conclusions are as follows:(1)When the grid spacing of WRF model is increased from 9km to 3 km,the genesis process of the tropical cyclone becomes slower.The Cumulus Parameterization does not make sense in the 3km domain and the microphysics scheme plays the role in simulating the moisture processes.The great value of vertical velocity at the particular grids will makes the convective-scale(removing the area average component)vertical momentum advection at low-level twice on average as much as that in control run,which results in the decrease of low-level vertical shear in the fine-grids experiment.In addition,the increase of great value points of vertical velocity makes the CAPE consumed rapidly.The absence of CAPE and low-level vertical shear both pose negative contribution on the development of convections and finally lead to the delay of tropical cyclone's formation.This study demonstrates that there are still some problems in simulating the convections.Even the most advanced mesoscale model(WRF)in the world is hard to simulate the real formation process of tropical cyclones.(2)When the data with a resolution of 1hr in time and 3km in space is used in calculating the speed of a tropical cyclone with the PVT method,the PVT speed is similar to the speed of the tropical cyclone.If the resolution in time remains unchanged and the resolution in space increases to 333m,the deviation between PVT speed and the speed of the tropical cyclone comes up to 100%.If the resolution in time is increased to 1min at the same time,the deviation can decrease to about 13.5%.When the resolution in time(1hr)is unchangeable,the deviation between PVT speed and speed of the tropical cyclone can be reduced by smoothing the original physical fields,used in calculating PV,in space.This study shows that when we use the data of different resolutions in time and space to calculate the speed of tropical cyclones with PVT method,different results can be received.Preprocessing of data may be needed in according to the purpose of the very study.