Horizontal divergence of typhoon-generated gravity waves in the upper troposphere and lower stratosphere (UTLS) and its influence on typhoon evolution

摘要

The characteristics of horizontal divergence induced by typhoon-generatedgravity waves (HDTGWs) and the influence of HDTGW on typhoon evolution areinvestigated based on the simulation results of Typhoon Saomai (2006) usingthe Weather Research and Forecasting (WRF) model. The power spectral densityof HDTGW shows dominant powers at horizontal wavelengths of 20–30 km and atperiods of less than 1 h. This is associated with gravity wavesgenerated by vigorous convective clouds in an inner core region of thetyphoon. However, the domain-averaged HDTGW in the upper troposphere andlower stratosphere had a spectral peak at 24 h, which is well correlatedwith the minimum sea-level pressure of the typhoon, especially during arapidly developing period. The 24 h period of the averaged HDTGW stemsfrom the inertia–gravity waves generated by the convective clouds in thespiral rainbands, and showed no clear association with the thermal tides orthe diurnal variation of precipitation.