THE COMPARATIVE ANALYSES OF CIRCULATION CHARACTERISTICS AND THEIR EFFECT ON PRECIPITATION OVER LIAODONG PENINSULA ASSOCIATED WITH TYPHOONS TURNING WESTWARD OVER YELLOW SEA

Based on the Tropical Cyclone Yearbook and the NCEP/NCAR reanalysis data,large scale circulation characteristics are analyzed for two typhoons(7203 and 7416),which turned westward suddenly over the Yellow Sea and have the same tracks but distinct rainfall intensity in 24 h.Typhoon 7203 produced more than twice as much rainfall as Typhoon 7416,although it didn't pass near the Dalian area as Typhoon 7416 did.The results show that transport of water vapor in the southwestern or southeastern air stream is crucial to typhoon rainfall.A deep southwestern or southeastern jet is usually associated with a heavy-rainfall typhoon for a long time even after its landfall.Basically,strong-rainfall typhoons moving northward are characterized by strong divergence at upper levels.It extends into the upper troposphere and cyclonic circulation and strong ascending drafts are maintained steadily.Downward propagation of westerly momentum in the upper-level jets is favorable for maintenance of typhoons.After the landfalling typhoons turn to the west,energy lost due to frictional dissipation effect of ground surface will be compensated for from the mid-latitude environment,which is favorable for the inducing and maintenance of heavy rain.The instability and conditions of the warm and moist atmosphere in the region of typhoon tracks can also affect the rainfall intensity.