湖北省三次春季暴雨过程水汽来源与输送特征分析

Analysis of Moisture Source and Transport Pathway of Three Rainstorms in Hubei Province in Spring

利用常规观测资料、地面加密资料,先分析了2017年4月8—9日、2005年4月8—9日和2019年4月8—9日湖北三次暴雨过程(分别简称“2017年”“2005年”“2019年”暴雨过程,下同)的环流背景和主要影响系统;再利用HYSPLIT模式和NCEP 6 h一次的1°×1°再分析场模拟了三次暴雨过程中最强降水中心气块的后向轨迹,讨论了不同高度轨迹中的气块在移动过程中水汽的变化。得到如下结论:1)三次暴雨过程发生均在500 hPa槽东移的背景下,中低层有低涡、切变线、低空急流、地面冷锋等辐合系统,并伴有高空辐散,上升运动强、水汽充沛。2)三次暴雨过程的共同特征是水汽均主要来源于对流层中低层气块,特别是3000 m以下的气块水汽含量大,是暴雨过程水汽的主要贡献者;但气块的源地、移动路径和气块获得水汽的途径不同。三次暴雨过程中终点到达5000,7000和9000 m的气块均源自孟加拉国及其以西地区,向东或东北方向移向强降水中心,但水汽含量小;终点到达500、1500、3000 m的气块源地相对分散,即终点到达500 m的气块分别来自中南半岛北部、东海和暴雨区南侧的近地层,水汽含量最大;终点到达1500 m的气块,分别源自暴雨区的北侧、孟加拉湾东部和暴雨区南侧的近地层;水汽含量较大;终点到达3000 m的气块,分别源自黄海、西亚地区,仍有一定的水汽含量。“2017年”“2005年”暴雨过程中的气块主要从近海面获得水汽,其次是从陆地上获得水汽,而“2019年”暴雨过程中的气块主要是获得陆地蒸发的水汽。表明了暴雨过程中水汽来源和输送的多样性和复杂性。3)通过对三次暴雨过程的分析得到的预报启示是:在西风带高低空系统有利的配置下,除了关注副热带夏季风从南海输送水汽外,还要重视暴雨区本地及其周边地区近地层高温高湿环境中水汽的贡献。

Analysis of three rainstorms occurred on 8-9 April 2017,2005 and 2019 in Hubei province were carried out using conventional observations,hourly surface observation.192,120 and 144 h backward trajectories were simulated and studied based on HYSPLIT model and 6-hourly NCEP reanalysis data.(1)The results showed that three rainstorms happened with 500 hPa trough,vortex,shear lines,low level jets and cold front and divergence at 200 hPa.(2)In general,water vapor mainly comes from the middle-low troposphere during three rainstorms,especially below 3000 m and contributed more.But the source region,the movement and the way of picking up moisture of air parcels are different in three rainstorm processes.Air parcels ended up over 5000,7000 and 9000 m came from outside of China are dry air and contribute little.But air parcels ended up over 500,1500 and 3000 m originated from different areas.Air parcels ended up over 500 m came from the north of Indo China Peninsula,East China Sea and the south of rainstorm area with the highest specific humidity.Air parcels ended up over 1500 m originated from the north of rainstorm area,the east of Bay of Bengal and the south of rainstorm area with higher moisture.Air parcels ended up over 3000 m came from Yellow Sea and West Asia area with moderate water vapor.Air parcels picked up moisture mainly from sea surface,secondly from land surface in“2017”and“2005”cases,but air parcels picked up moisture mainly from land surface in“2019”case.There are diversity and complexity of moisture source and transport.(3)With the advantage of synoptic situation,beside the water vapor from South China Sea with subtropical monsoon,moist air from rainstorm area and its surrounding regions is very important.