Case Study On The Formation Of Warm Core Structure Of Typhoon In South China Sea And Preliminary Analysis On The Changing Character Of Warm Core Structure Of Typhoon Before And After Landing

Warm core structure is one of the most prominent feature of typhoon. Typhoon isa warm cyclonic circulation, the foundation of typhoon in upper air is one of themain symbols for typhoon formation.The changing character of warm core structurein two key periods of typhoon life span are studied preliminarily.Firstly, The changing character of warm core structure and its relationship withmaximum wind velocity and geopotential height of two typhoon in South China Seaduring their formations, which named as lingling(0123) in 2001 and Damrey(0518)in 2005, is analysised using NCEP/NCAR global tropospheric 1°×1°analysis, theresults show that: (1) The initial warm core, which has thin vertical range and smalltemperature gradient outside, was formed in the level of 300—400 hPa at uppertroposphere; (2)As the depression grows to typhoon, the intensity of warm coreincreased, also its vertical range extend to upper and middle troposphere, outsideisoline densified gradually, and outside temperature gradient increased; to the time oftyphoon numbering, classical warm core structure was formed: central temperatureanomaly reached maximum, in the narrow vertical band outside there is powerfulradial temperature gradient; (3)During the formation of typhoon, maximum windvelocity and maximum geopotential height anomaly (absolute value) are allincreased; (4) There are notable relationship among warm core,maximum windvelocity and geopotential height during the process of warm core formation.As thewarm core increased, maximum wind velocity and maximum geopotential heightanomaly ascended.Subsequently, the changing character of warm core structure of eight landingtyphoon before and after land-fall is analysised, the results suggest that: (1)Beforeand in land-fall, warm core structure is mature and strong; its vertical range whichcovered middle and upper troposphere is thick and strong; temperature gradient outside the center is very large, warm core structure is axisymmetric, after land-fall,warm core faint, vertical range reduce to about 300hPa from middle and uppertroposphere; temperature gradient outside the center is small, also the initialaxisymmetric structure fade and distort; (2)In the period of landing, the changesituation of warm core intensity can be divided into three kinds, the first kind, warmcore intensity reach maximum in 24h before land-fall, weaken at the moment ofland-fall, and continue decrease after landing; the second kind, warm core intensityincrease before land-fall, reached maximum at the moment of land-fall, and decreaseafter landing; the third kind, warm core intensity weaken before land-fall, increasea little after land-tall in 12h, then weaken; (3)Warm core intensity at the moment ofland-fall has obvious relationship with its maintenance after landing, warm core fadequikly after landing when it was weak at the moment of land-fall, warm core hold along time after landing when it was strong at the moment of land-fall.