Preliminary Analysis On The Characteristics Of Three-dimensional Structure Of Typhoon During Its Formations And Before Landfalling

The characteristics of three-dimensional structure of typical landfalling typhoonduring their formation and before landing, is diagnosed using the tropical cycloneyear- book from 2000 to 2006 and NCEP/NCAR global tropospheric 1°×1°analysis.First of all,as the background for next works,the comparations of tropicalcyclones between in northwest Pacific and landfalling China have been made inaspect of annual,monthly,and position changes.Secondly,the three-dimensional structure of two landfalling typhoon duringtheir formations,which named as Jelawat and Bilis in 2000,is discussed.The resultsshow that:During the typhoons' formation,the radius of maximum wind decreasedwith the increase of the maximum wind velocity.The vertical motion whichdeveloped from the mid-troposphere expanded to the upper and lowerlevels,respectively.At the same time,the intensity of vertical motion increased.On theother hand,the positive potential vorticity gathered gradually over the typhooncenter, and the physical variables changed more obvious at 850hPa and 500 hPa than300 hPa.The 3-D structure characteristics of the 14th typhoon named Rananim in 2004and 9th typhoon named Matsa in 2005 have been analyzed in a period of 48h atlandfalling and before. The diagnostic results show that,(1) The intensities of twotyphoons increase with their moving to the land in 48h,which are closely related tothe typhoons' axisymmetrication on lower-,mid-,and higher- level of troposphere,andthe mid- and small-scale vortices around typhoons' circulation; (2) The evolution ofeach physical quantities of typhoons presents the tendency that rotates anti-clockwisearound the center on surface of Rananim and Matsa respectively,which result in themain convection and big wind velocity area locate the northeast to the center onsurface of Rananim and Matsa.