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引发舟曲特大泥石流灾害强降雨过程成因
引用本文:钤伟妙,罗亚丽,张人禾,宫宇.引发舟曲特大泥石流灾害强降雨过程成因[J].应用气象学报,2011,22(4):385-397.
作者姓名:钤伟妙  罗亚丽  张人禾  宫宇
作者单位:中国气象科学研究院灾害天气国家重点实验室,北京 100081
基金项目:资助项目:中国气象科学研究院灾害天气国家重点实验室自主研究课题(200204001002019)
摘    要:利用自动气象站观测资料、MTSAT卫星红外亮温资料、NCEP/NCAR再分析资料、AIRS卫星大气温湿资料、MODIS卫星气溶胶光学厚度资料和ECMWF模式预报的地面风、压、温、湿资料,对2010年8月7—8日甘肃省甘南州舟曲县引发特大泥石流灾害的强降雨天气过程的成因进行了天气动力学诊断分析,结果表明:由于地表强烈增温与高空槽后冷空气平流作用,8月7日午后舟曲及其上游 (西北方向) 地区大气不稳定性极强,区域平均对流有效位能 (CAPE) 值为4393 J·kg-1、对流零浮力层 (LNB) 高度达16.54 km;南北气流交汇与局地复杂小地形使得近地面形成多个中小尺度辐合线和辐合中心,于8月7日14:00(北京时) 左右触发了对流的产生;强盛的西北太平洋副热带高压与台风电母之间的偏南气流在23°~30°N纬度带转向西输送水汽直达青藏高原东缘,在高原地形作用下转为向北传输到达舟曲附近区域,为该区域对流发展提供水汽条件;对流云团形成后,在高空西北气流的引导下向东南方向移动,于8月7日夜间到达舟曲地区造成该地区强降雨,引发特大泥石流灾害。

关 键 词:青藏高原    对流零浮力层    湿静力能    中尺度辐合
收稿时间:2010-10-14

The Heavy Rainfall Event Leading to the Large Debris Flow at Zhouqu
Qian Weimiao,Luo Yali,Zhang Renhe and Gong Yu.The Heavy Rainfall Event Leading to the Large Debris Flow at Zhouqu[J].Quarterly Journal of Applied Meteorology,2011,22(4):385-397.
Authors:Qian Weimiao  Luo Yali  Zhang Renhe and Gong Yu
Institution:State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081
Abstract:Heavy rainfall occurs abruptly at Zhouqu, Gansu Province at night of 7 August 2010, causing disastrous debris flow and bringing about more than a thousand casualties. To find out the possible triggering mechanism of this rainfall, observations by Automatic Meteorological Stations are used to analyze temporal variation of the surface temperature and spatial distribution of rainfall; brightness temperature data from MTSAT satellite are adopted to reveal evolution of convective clouds; NCEP/NCAR 1°×1° reanalysis data are used to investigate the large-scale atmospheric conditions; AIRS satellite observations are examined to analyze the atmospheric instability; and ECMWF 0.125°×0.125° forecast data are employed to study the convection. First, over Zhuoqu and its upstream (northwest) region, the rapid increase of surface air temperature and the cold air advection in the rear area of the upper-level trough significantly enhanced the conditional instability in the morning of 7 August, favoring formation and development of deep convection. Second, several small-scale convergence centers and lines at the ground surface, generated by interactions among the southerly warm and northerly cold air flow near the ground surface and the complex terrain elevation, triggered the formation of the precipitating convective clouds around 14:00 7 August 2010 (Beijing Time). Third, the southerly air flow between the strong Northwest Pacific Subtropical High and the typhoon "Dianmu" changed to easterly at 23°—30°N, transporting water vapor toward the west until reaching the eastern side of Tibetan Plateau, and then changed to northward, supplying abundant moisture for the raining storm over Zhouqu and its upstream region. At last, the convective clouds moved toward southeast following the upper-level air flow, arrived at Zhouqu and produced heavy rainfall at night of 7 August, leading to the large debris flow at Zhouqu.Satellite remote sensing observations play an important role in the diagnosis of this synoptic process. The infrared brightness temperature (TBB) from the MTSAT satellite reveals the occurrence, development, movement and weakening of the convective clouds which directly produced the heavy rainfall at Zhouqu. The air column temperature and moisture data observed by the AIRS satellite around 14:30 7 August 2010 are used to analyze convective available potential energy (CAPE) and level of neutral buoyancy (LNB) height. The results indicate that atmosphere over Zhouqu—Qinghai Lake region is strongly unstable with the area-averaged CAPE of 4393 J·kg-1 and LNB height of 16.54 km.
Keywords:Tibetan Plateau  level of neutral buoyancy  moist static energy  meso-scale convergence  
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