Potential enstrophical diagnostic analyses on the mechanism of change of tropical cyclone intensity

It is indicated that the change of mean potential enstrophy within tropical cyclone(TC) corresponds to the change of TC intensity.A series of factors influencing the intensity change have been discussed by calculating budget of potential enstrophy in tangential wave-number domain in cylindric coordinates.The results indicate that the vertical distribution of mean diabatic heating is an important factor that influences the change of TC intensity through transformation mechanism of the Coriolis effect and cyclonic vorticity,especially in the sudden intensifying stage of TC.It is favourable to the intensification when the diabatic heating is largest in upper-middle troposphere,while TC weakens when this kind of role of heating become small or the heating is largest in lower troposphere.The role of the axisymmetric fields of TC is different from that of the non-axisymmetric fields.In addition,we have analysed some other factors that influence TC intensity.