A NUMERICAL STUDY ON VORTICITY PROPAGATION AND CHANGES IN TYPHOON INTENSITY^*

An f-plane quasi-geostrophic barotropic vorticity equation model of high resolution is designed in this paper in order to investigate the characters of vorticity propagation and the effect of nonlinearity on the propagation within a typhoon circulation,wherein two mesoscale vortices coexist at different radial positions.The results of 10 sets of experiments suggest that in comparison with only one vortex,the intensity of the inward propagations of vorticity strengthens distinctly,vorticity detains in the inner region of typhoon circulation for a longer time,and the local maximum wind speed in the inner region increases clearly.The introduction of nonlinear advection into the model weakens the intensity of both inward and outward propagations of vorticity,but makes the inward propagation up to a position closer to the center of typhoon.