桂北山区一次持续性暴雨的水汽输送特征

利用常规观测资料、区域自动站资料、NCEP/NCAR逐6 h再分析资料，对2021年6月28日~7月4日柳州持续性暴雨的环流形势和水汽输送特征进行了分析。结果表明：500 hPa南支槽和副热带高压的对峙导致850 hPa低涡切变稳定少动，为暴雨区建立了稳定、持续的水汽通道；南海夏季风的爆发为暴雨区提供源源不断的水汽，水汽输送大值带主要位于700 hPa以下，以边界层925 hPa水汽辐合最强；从水汽收支看，南边界为主要水汽输入边界，东边界则为水汽主要输出边界，越往高层水汽出流越明显；南边界水汽输入对于区域水汽净流入的贡献主要在700 hPa以下，且越往低层南边界水汽贡献越明显；柳州北部元宝山脉对水汽的流出有一定阻挡作用，925 hPa以下北边界的水汽流出比南边界的流入小一个量级。

Analysis of Water Vapor Transport Characteristics of a Sustained Rainstorm in Mountainous Areas of Northern Guangxi Province

Based on conventional observation data, regional automatic station data, NCEP/NCAR 6-hourly reanalysis data, the circulation pattern and water vapor transport characteristics of a persistent rainstorm in Liuzhou from June 28 to July 4, 2021 are analyzed. The results show that: The confrontation between the southern branch trough at 500 hPa and the subtropical high made the vortex shear at 850 hPa become stable and less dynamic, thus establishing a stable and sustainable water vapor channel for the rainstorm area. The outbreak of the South China Sea summer monsoon provided a continuous stream of water vapor for the rainstorm area, and the maximum value belt of water vapor transport was mainly below 700 hPa, with the water vapor convergence in the boundary layer being the strongest at 925 hPa. In terms of water vapor budget, the southern boundary was the main input boundary of water vapor, while the eastern boundary was the main output boundary of water vapor, and the higher the water vapor flowed, the more obvious it was. The contribution of water vapor inflow at the southern boundary to the regional water vapor inflow was mainly below 700 hPa, and the contribution became more obvious at the southern boundary at the lower layer; The Yuanbao Mountain in the north of Liuzhou blocked the water vapor outflow, therefore, the water vapor outflow at the northern boundary below 925 hPa was one order of magnitude less than the water vapor inflow at the southern side.