台风“天鹅”远距离暴雨的水汽条件分析

Analysis on Water Vapor of Far Distance Typhoon ‘Goni'

为了研究远距离台风降水的水汽特征,利用NCEP/NCAR(1°×1°)再分析资料和常规高空、地面观测资料等对2015年第15号台风"天鹅"(Goni)的水汽分布特征和变化特征进行了分析,该台风在北上过程中对中国长三角中部地区的降水产生影响,是一次典型的远距离台风降水。分析结果表明:(1)本次降水是在高空急流轴入口右侧的槽前发生的,台风东侧强的气流将水汽输送至500 h Pa高空槽前,暖湿气流与槽后南下的干冷空气相遇形成降水。(2)暴雨主要由短时强降水构成,强降水时段最大降水中心位于5840 gpm等高线上。(3)整层水汽含量峰值出现在强降水时段之前,台风中心强度的变化影响着降水区整层水汽含量的变化,且中心气压越低,可降水量值越高,暴雨区降水强度越大。(4)强降水之前湿层较厚,比湿和辐合增强,水汽通量散度负值中心与上升运动中心基本吻合,有利于水汽的辐合上升,对降水的维持和增幅都起到了积极的影响。

To the haracteristics of water vapor in a far distance typhoon rainfall, NCEP/NCAR （1°×1°） reanalysis data and conventional observational data are used to investigate the distribution and variation of water vapor in No. 15 Ty- phoon ＇ Goni＇ in 2015. It impacts on the precipitation in the middle of China＇s Yangtze River Delta during its moving north, and it is a typical fardistance typhoon rainfall. In this paper, The results show that the precipitation occurs in the front of the trough, which is on the right side of the entrance to the upper jet axis. The airflow on the east side of the ty- phoon makes water vapor transport to the front of trough at the 500 hPa, and warm and wet airflow meets the cold and dry down from south of the back trough, which plays a positive role in maintaining the heavy rains. The heavy rainfall is mainly made up by severe short-range precipitation, and the maximum center of heavy rainfall locates on the isoline of 5840gpm. The peak value of moisture content of the whole layer appears before the severe short-range precipitation. The changes of intensity in the typhoon＇ s center the moisture content of the whole layer in the precipitation zone. What＇ s more, the lower central pressure, the higher PW and the greater intensity of precipitation in rainfall areas. Wet layer is thick, and specific humidity and convergence become str before heavy rain. The negative center of vapor flux divergence substantially coincides with ascending motion＇ s center, which is beneficial to water vapor convergence. And it s a posi- tive impact on the maintenance and increase of precipitation.