| Focusing on two noticeable typhoons, the17th("NESAT") and9th("MUIFA"),which affect Chinese coast in the summer of2011, this paper collects satellite images,analysis500hPa observation field with synoptic methods, to find out the reasons whytheir movements and intensity changed near China offshore. Furthermore, based on thedynamic theory of potential vorticity advection equation, using reliable andhigh-resolution reanalysis data, diagnostic analysis of temporal and spatial change forboth potential vortex advection and heating field in upper-air were studied. Mainconclusions are follows:The negative and positive center of potential vorticity advection synthetic field islocated in north and south of the typhoon center, with cyclonic and anti-cyclonictransport of potential vorticity advection correspondingly. When the positive center ofPV advection moves southward and gets close to the center of typhoon,"NESAT" willmove toward western slightly. The positive and negative regions of heating field aregenerally located in the northwest and southeast of the center of "NESAT". If thisdistribution begins to rotate counterclockwise around the center of the typhoon,"NESAT" will shortly deviate westward from its northwest movement before.Moreover, because of the weak atmosphere circulation background, the heatingdistribution of "MUIFA" could indicate the moving direction of typhoon center. Thepositive heating field center is often in the front right side of the typhoon. Following theshift of heating field positive center toward a certain direction, possibility of "MUIFA"moving toward that direction will increased. In addition, the symmetry of heating fielddistribution and the concentration of the heating field contours are corresponding to theconvection intensity of the typhoon wall cloud. |
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