两次严重影响湖南的登陆台风水汽场特征数值模拟

Numerical study on the Water Vapor Transports of the Two Landfalling Cyclones Affecting Hunan Province

针对造成湖南省特大暴雨过程的"碧利斯"和"圣帕"两次台风,利用气象、水文加密观测资料及NCEP再分析资料,结合中尺度数值预报模式AREM的模拟结果,对它们独特的水汽场特征进行了对比分析。结果表明:这两次台风的共同特点是有两条主要水汽输送通道,即与西南季风相联系的偏南风水汽通道和与台风低压环流相联系的偏北风水汽通道;凝结降水的水汽主要来源于低层风场辐合和水汽平流,并通过局地垂直运动再将其输送到中高层;在湘东南强降水区上空始终存在强的水汽水平辐合和水汽垂直输送,比较而言,"圣帕"台风暴雨区上空水汽通量更强,但水汽通量辐合强度却小于"碧利斯"台风,水汽辐合层也不及后者深厚,但前者由于自身旋转性强,低压环流中心南部的切变较长时间维持,并自东向西转动,使得强降水持续时间更长,过程雨量更大,影响范围也更大。"碧利斯"水汽主要源地较"圣帕"更加偏南,水汽辐合更强,与南海季风的相互作用更显著,降水时段集中,局部地区短时间内的降雨强度甚至超过了"圣帕"。

Based on the multiple meteorological, hydrological intensify observations, and the NCEP reanalysis data, combined with the simulation and diagnosis data of meso-scale numeric model of AREM, the water vapor features of two unique cyclone, the typhoon Bills and Sepat which inducing heavy rainfall in the Hunan province are analyzed and some comparisons are conducted. The results show that, both of cyclones have two main water vapor channels, one is from south linking with the west-south monsoon, and the other is from north linking with the cyclone＇s low-pressure circulation. In addition, their rain water mainly originates from the convergence of the lower levels, and is transported to the middle and high levels by local ascending airflows. However, it is noted that the water vapor flux in the Sepat＇s heavy rain areas has stronger intensity than that of Bilis. Although with the weaker convergence of the water vapor flux and thinner convergent depth, Sepat＇s lifetime is longer, total rainfall is larger and covering area is broader, since it has relatively stronger inner strength, and the steady wind shear in the south part of the cyclone＇s center. On the other hand, the main water vapor path of Bilis is much more southerly, the moisture convergence and the interaction of the South China Sea monsoon are stronger than those of Sepat＇s, its rain intensity in some areas and in certain periods is much more stronger.