2017年川东北首场暴雨过程水汽条件分析

本文利用NCEP1°×1°6小时再分析资料及常规观测资料，针对2017年5月2～3日发生在四川盆地东北部的一次暴雨天气过程的水汽条件进行分析。其结果表明:(1)暴雨开始前，水汽含量猛增，湿层厚度增加，并在整个过程中维持高湿状态；暴雨区水汽随时间由南向北逐渐增加。(2)暴雨区水汽总收支在整个时段都为正值，水汽收入大值与两个降水时段的开始时间重合，经向的水汽输入在此次过程中起主要作用。(3)水汽的来源主要是孟加拉湾和南海，水汽输送以850～700hPa为主，由南至北逐渐减弱，南部湿层更厚，与大暴雨落区相对应。(4)第一阶段降水开始时，水汽低层辐合、高层辐散，两阶段降水之间辐合减弱，然后又增强并持续到过程结束。 

Analysis of the Water Vapor Condition during the First Rainstorm in 2017 in Northeast Sichuan

Use NCEP 6-hour reanalysis data (1°×1°)and conventional observation data to analyse the water vapor condition of a rainstorm process in northerast Sichuan in May 2～3, 2017.The results show that:(1) Before the rainstorm started, the water vapor content soared, the thickness of wet layer increased, and maintained in the whole process of high humidity; The water vapor in the rainstorm increased gradually with the time from south to North.(2) The total amount of water vapor in the storm area is positive for the whole period, and the large value of water vapor revenue coincides with the beginning time of the two precipitation periods, the meridional water vapor input plays a major role in this process.(3) The main sources of water vapor are the Bay of Bengal and the South China Sea and the water vapor transport is dominated by 850～700hPa, gradually decreasing from south to north, the southern humid layer is thicker and corresponds to the heavy rainfall area.(4) In the first stage of precipitation, water vapor convergence of low-level and divergence of high-level, the convergence between the two stages of precipitation is weakened and then enhanced and continues until the end of the process.