Diagnostic analysis of largesca le circulation features associated with strong and weak landfalling typhoon prec ipitation events.

Based on the Tropical Cyclone (TC) Yearbook, the NCEP/NCAR reanalysis data and t he dynamic composite analysis, largescale circulation characteristics are anal yzed for two kinds of typhoons, the strongrainfall typhoon (SRT) and the weak rainfall typhoon (WRT), which have tracks and TC intensity but distinct rainf all intensity in 48 h after the typhoon landfall. The results show that, transport of water vapor in the southwestern air stream is crucial to typhoon rainfall. A deep southwestern jet is usually associated with a SRT for a long time even a fter its landfall. Basically, SRTs are characterized by strong divergence at upper levels. They extend into the upper troposphere and the cyclonic circulation a nd strong up drafts are maintained steadily. The instability of atmosphere in th e downstream region of the typhoon before its landfall can also affect the rainf all area and intensity. Warm and moist atmosphere is favorable for the intensifi cation and maintenance of heavy rain due to the supplement of total energy espec ially the latent energy. Therefore, large-scale circulations have a significantimpact on typhoon rainfall. The largescale features such as the depth and int ensity of the southwestern air stream linking with the typhoon, the intensity of low-level convergence and upper-level divergence, the environmental wind stru cture of the typhoon circulation, and the thermodynamical and humidity condition of the environmental atmosphere, should all be taken into consideration in orde r to correctly forecast typhoon precipitation.