A PRELIMINARY ANALYSIS ON MECHANISM OF SIZE CHANGE IN TROPICAL CYLONE

By using the WKB method and slowly-varying wave packet theory the maincause for the sisechange in tropical cyclones is analyzed. It is shown that the size change in tropical cyclones is mainly determined by the inner factors. In general case the angular frequencies of inertio-gravity waves are positive, thus provided that both stratification and inertia are stable, when the parameters of inertial andstatic stabilities increase with the distance from the centre, the sise gets larger; when the parameters of inertial and static stabilities decrease with the distance from the centre, the size gets smaller. The for mer may be called the "expanding" of tropical cyclones and the latter may be called the "shrinking" of tropical cyclones.