2012—2018西藏“雨窝”降水特征及其成因分析

Characteristic and Causal Analysis of Concentrated and Frequently Occurring Intense Rainfall in Tibet in 2012-2018

本文采用2012—2018年西藏74个气象站的降水资料,以及墨脱站小时、日、月、季、年的降水资料,对西藏的降水日数、累计降水量、强降水的空间分布进行了分析,结果表明:(1)墨脱是西藏降水日数最多、累计降水量最大的中心,也是出现极端强降水概率最高的区域。(2)墨脱的降水主要集中在3—10月,降水呈现双峰型,峰值分别出现在6月和9月,其中9月的降水量跟年降水量有很好的相关性。(3)墨脱出现暴雨次数最多的是5、8、9月,其中5月的暴雨日数突增,与8、9月的暴雨日数相当。(4)墨脱干湿季分明,多夜雨,凌晨03:00—07:00出现降雨的概率达到50%以上。墨脱位于西藏的最南端,海拔从最低的115m上升到1200m,印度洋的湿润气流沿着雅鲁藏布河谷长驱直入,在地形抬升作用下,使得墨脱的降水量堪比同纬度的内地沿海城市,因此墨脱为西藏的"雨窝"。

This paper adopts the precipitation data of 74 meteorological stations in Tibet from 2012 to 2018,as well as the hourly,daily,monthly,seasonal,and annual precipitation data of Modog Station to analyze the spatial distribution of precipitation days,cumulative precipitation,and intense rainfall in Tibet.The results show that Medog is the precipitation center of Tibet,with the most precipitation days and the largest accumulated precipitation,and it is also the area with the highest probability of extreme intense precipitation.The precipitation in Medog is mainly concentrated from March to October,and the precipitation presents a dual-peak pattern,with peaks appearing in June and September,respectively.The precipitation in September has a high correlation with the annual precipitation.The rainstorms occur most frequently in Medog in May,August,and September.The number of rainstorm days increases sharply in May,which was equivalent to the number of rainstorm days in August and September.The dry and wet seasons of Medog are distinct,and there occur night rains frequently.The probability of rainfall from03:00 to 07:00 presents 50% or above.Medog is located at the southernmost tip of Tibet,with the altitude rising from the lowest 115 meters to 1200 meters.The humid air currents from the Indian Ocean drive along the Yarlung Zangbo Valley.The uplift of the terrain makes the precipitation in Medog comparable to that of coastal cities at the same latitude in China.