登陆过程中台风高层暖心结构演变特征分析

采用美国国家环境预报中心NCEP提供的分辨率为0.5°的再分析资料和中国气象局上海台风研究所热带气旋最佳路径集,对1979—2010年于30°N以南登陆中国的台风进行合成并分析其高层暖心结构,主要结论如下:(1)登陆台风暖心在登陆前18h左右强度有较明显的加强趋势;(2)登陆阶段台风暖心有着明显的非对称性,向陆地侧的暖心面积更大;而在登陆方向两侧暖心结构也存在较弱的非对称性,登陆前暖心面积左侧大于右侧,登陆后暖心面积右侧大于左侧。(3)登陆台风暖心的温度梯度分布是不均匀的。越靠近暖心外围,温度梯度越大,越靠近暖心中心,温度梯度相对较小。当暖心强度变化后,暖心内层温度的变化率大于外层。(4)登陆过程中暖心强度在垂直方向的衰减比水平方向更为显著。(5)文中几种台风暖心特征的计算简便,物理含义明确,为实际业务提供了较为不错的定量化参考,方便理解台风暖心结构与台风强度变化之间的关系,具备一定的业务应用价值。

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.