热带气旋进入北部湾后强度增强的环流特征分析

利用NCEP/NCAR再分析资料,对1949年以来7个进入北部湾后强度突然增强的热带气旋(TC)环流背景特征及物理量场特征进行分析,结果表明,有利TC进入北部湾后强度增强的环流背景是:(1)西太平洋副热带高压稳定加强西伸,(2)热带辐合带北抬至华南沿海活动,(3)西南季风爆发处于活跃期,(4)东风波西移叠加,(5)有适度的弱冷空气侵入;对物理量场的合成分析表明,TC进入北部湾前和进入北部湾后,环流中心附近500hPa涡度变化极小,200hPa高空散度增大,500hPa垂直上升速度增大,850hPa中南半岛水汽输送量增大。

Analysis of the Atmospheric Circulation of TC enhancement after into the Beibu Gulf

Based on NCEP reanalysis data,there are seven cases since 1949 of the tropical cyclones increased suddenly after coming in Beibu Gulf.The characteristics of their circle situations and physics field are conducted.Results show that there are five conditions useful to TC enhances suddenly:(1) the sub-tropical high over the west Pacific extends to the west;(2) the tropical convergence moves northward and stays along the coast in South China;(3) Southwesterly monsoon keeps active;(4) the easterly wave moves westward and mixed with the other synoptic system;(5) appropriate amount cold air invades.composition analysis of the physical field indicate that the vorticity on the cycle center at 500 hPa is almost a constant before and after TC into Beibu Gulf while the divergence at 200hPa and verticity at 500hPa and the moisture over the Indochina Peninsula at 850hPa increased.