登陆华南热带气旋强度变化与大尺度环流的关系

应用UK再分析资料，采用合成分析方法，对比分析了登陆华南的登陆前迅速增强的TC（Rapid Intensifying TC，简称RITC）和迅速减弱的TC（Rapid FillingTC，简称RFTC）登陆前24h的大尺度环流背景特征。结果表明：从外流、入流强度和范围上看，RITC的低空入流和高空外流均明显强于RFTC，两类TC高空外流强度的差异比低空入流明显，RITC的次级环流径向范围大；从外流垂直伸展高度上看，RITC的平均外流主要集中在500hPa以上，而RFFC的平均外流比较分散，向下伸展到850hPa；从高空流场配置看，RITC上空除西北象限外均有较强外流，而RVrC仅在东北象限有较强外流，相应的RITC和RVrC的高空辐散在范围和强度上均有明显的差异，其中RITC的高空辐散明显强于RFTC；强烈的西南季风水汽输送是登陆华南的TC登陆前突然加强的先兆条件，RITC的对流活动明显比RFTc活跃；RITC的纬向风垂直切变比RFTC小，有利于RITC的强度增强。

Relationship between intensity change of tropical cyclone landing in South China and large-scale circulation

Based on the UK reanalysis data, this paper studies and compares the large-scale environmen- tal characteristics of Rapid Intensifying TC （RITC） and Rapid Filling TC （RITC） at 24 h before land- ing in South China by using the composite analysis method. Results show that the low level inflow and upper level outflow of RITC are significantly stronger than those of RFrC, the intensity difference in high level outflow between RITC and RP-TC is more significant than that in low level inflow, and the secondary circulation radial range of RITC is larger than that of RFTC. In terms of the vertical stretc- hing height of outflow, the average outflow of RITC is concentrated on levels above 500 hPa, while the average outflow of RFFC is dispersedly spread down to 850 hPa. The analysis of high level flow field indicates that RITC has stronger high level outflow except in the northwest quadrant, while RFFC only has stronger high level outflow in the northeast quadrant. Correspondingly, there are obvious differences in the range and intensity of upper level divergence between RITC and RFTC,in which the upper level divergence of RITC is stronger than that of RFTC. The abundant southwest monsoon water vapor trans- portation can promote TC intensifying rapidly before landing in South China, and the convective activity of RITC is obviously stronger than that of RFTC. The tropospheric vertical wind shear of RITC is wea-ker than that of RFTC, which is beneficial to the intensifying of RITC.