Evolution of Warm-Core Structure in Upper Level of Landfalling Typhoons
Based on the 0.5° reanalysis data of National Centers for Environmental Prediction (NCEP) and typhoon best track data from China Meteorological Administration-Shanghai Typhoon Institute (CMA-STI), the warm-core structure of upper level in typhoons making landfall in China during 1979-2010 are diagnosed. The results of this study are shown as follows. (1) The intensity of landing typhoon cases always strengthens at the moment of 18 h before landing. (2) The structure of warm-core shows a remarkable asymmetry during landing, and the area of the onshore part is more remarkable. In the coastline region before landing, the warm-core structure is slightly asymmetrical in both left and right sides. And the left half of landing typhoons will go on developing until landing, and vice versa. (3) The distribution of warm-core temperature gradient is non-uniform. The closer to the periphery, the bigger the temperature gradient is. And in the inner core area, the temperature gradient is much smaller. When the intensity of warm-core changes, the change rate of central temperature is increased. (4) The warm-core intensity would decay more tempestuously in vertical direction in the landing process. (5) The several calculation methods proposed in this paper for the typhoon warm-core feature are relatively simple, and the physical meaning is very clear as well. When data is not complete or computational time requirements of operational forecast is higher, it can provide relatively better quantified reference, and especially help understand the relationship between typhoon warm-core structure and variation of typhoon intensity. Thus, it could have practical application values.