摘要
1981年7月9—14日岷江、沱江、涪江和嘉陵江流域出现持续性暴雨,并在四川省造成了历史上最严重的洪涝灾害。该文利用逐日降水资料、NCEP/NCAR 2.5°×2.5°逐日再分析资料和日本GMS卫星资料反演的TBB资料进行诊断分析以探讨此次暴雨持续的原因。结果表明:由于对流层低层的暖平流和其他大尺度强迫,高空槽长时间维持在长江上游地区,有利于槽后冷空气下沉南伸,与来自孟加拉湾的暖湿气流在盆地交汇,致使西南涡东移甚慢,于7月11—14日活跃在四川盆地上空。当西南涡沿梅雨锋缓慢东移时,长生命史的中尺度对流系统(MCS)在岷江、沱江、涪江和嘉陵江流域连续多次生消,导致暴雨系统持续维持在这些地区。大尺度的强迫在暴雨区上空产生了大范围持续性的上升运动,而暴雨所需的强上升运动主要由大量局地对流有效位能释放提供。对流层低层持续的水汽辐合和位势不稳定能量的输送则为暴雨的持续提供了充足的水汽和能量。与2004年9月发生在四川盆地东部的严重致洪持续性暴雨比较发现,虽然两次持续性暴雨发生的环流背景不同,但暴雨发生的物理机理一致,暴雨过程中持续性的上升运动均主要由大尺度强迫等引起,而且两次持续性暴雨的发生均与来自孟加拉湾的强水汽输送有关。
Persistent heavy rain occurs in Min River valley, Tuo River valley, Jialing River valley, Fu River valley in Sichuan Province during 9--14 July 1981 and causes a historic flood. To better understand the causes of the persisting heavy rains, diagnostic analyses are given by using rain gauge data from the meteorological stations in the Sichuan Basin, daily 2.5°×2.5° grid reanalysis data from NCEP/NCAR at 00-00 （UTC）, 06.00, 12.00 and 18.00 as well as TBB data every 3 hours derived from the Japanese Geostationary Meteorological Satellite （GMS）. The findings suggest persistent rainstorm causing serious flood in the Sichuan Basin lie in front of 500 hPa short wave troughs; isentropic potential vortex analysis shows that cold air from the rear of the persisting upper-layer trough northwest of the Sichuan Basin sinks southward and converges with warm and wet air from the Bengal Gulf, which causes the south vortex lagged in the basin during 7--14 July, when the Southwest Vortex slowly propagates eastward from Ya River and Min River in the west of Sichuan Basin to Tuo River, Fu River and Jialing River along the Meiyu front during 11--14 July, meso-scale convective systems （MCSs） generate and detain in the same areas, which is the direct cause for persistent heavy rainfall. Due to the warm advection in the lower troposphere and other large-scale forcing, the upper troughs maintain over the upper reaches of the Yangtze River and the Southwest Vortex slowly moves eastward along the Meiyu front, they bring continuous large-scale lifting movement in the heavy rainfall area; the strong lifting of the rainstorm systems is provided by the plenty local convective available potential energy （CAPE） release; continuous moisture convergence and potential instable energy transportation in the lower layers provide enough water and energy for the lasting heavy precipitation over the rainstorm area.
Compared with the famous flood-producing persisting heavy rainfall event in the east of Sichuan Basin in September 2004, it is found that though the synoptic circulation backgrounds are different, the physical mechanics of rainstorms are the same, that is, there are enough moisture and convective available potential energy in the instable air before the rain; CAPE transforms into the strong uplifting and rainstorm-producing MCSs develops quickly during rainfall; and large-scale forcing provides lasting uplifting to maintain rainfall; the two persistent heavy rainfalls in Sichuan Basin are related to the strong moisture transport from the Bengal Gulf. Therefore monitoring moisture from the Bengal Gulf is useful to forecasting such heavy rainfalls.
出处
《应用气象学报》
CSCD
北大核心
2006年第B08期79-87,共9页
Journal of Applied Meteorological Science
基金
国家重点基础研究发展规划项目(2004CB418301)资助
