Journal of Arid Meteorology

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Characteristics of Heavy Rainfall in Eastern Hexi Corridor on June 27, 2012

  

  1. 1.Wuwei Meteorological Bureau of Gansu Province, Wuwei 733000, China;
    2.Lanzhou Centerl Meteorological Observatory, Lanzhou 730020, China
  • Online:2015-12-31 Published:2015-12-31

河西走廊东部“6.27”突发性暴雨特征与成因

  

  1. 1.甘肃省武威市气象局,甘肃 武威 733000;2.兰州中心气象台,甘肃 兰州 730020
  • 作者简介:李玲萍(1977- ),女,汉族,甘肃定西人,高级工程师,硕士,主要从事天气、气候预报和研究工作. E- mail:wwqxjllp@163.com
  • 基金资助:

    甘肃省气象局英才计划:集合预报产品在暴雨预报中的应用

Abstract:

A heavy rainfall occurred in eastern Hexi Corridor on 27 June 2012 which triggered floods in 20 villages and towns and mudslides in several places, and caused the direct economic loss of over 17 million yuan. The heavy rainfall process mainly concentrated from 05:00 to 09:00 on June 27, 2012, and the maximum rainfall intensity was 19.1 mm/h and the 24-hour precipitation was 44.1 mm, so its prediction was very difficult. Based on the hourly precipitation from 82 regional stations and 6 automatic meteorological stations, Micaps conventional data, FY-2D satellite cloud images and NCEP/NCAR reanalysis data with 1°×1° spatial resolution, the characteristics of the heavy rainfall process were comprehensively analyzed from weather pattern, the upper and lower level jets, moisture condition, meso-scale unstable conditions and vertical motions. Results are as follows: (1) The large scale circulation characteristic of the rainstorm was typical ‘north-trough with south-vortex’ type. During the cold trough over Lake Baikal on 500 hPa moving southeastward,the cold air invaded into the back of Qaidam vortex and intersected in middle-eastern Hexi Corridor. At the same time, the stabilizing and sustaining of saddle field provided background for Qaidam vortex, then strengthened the low-level front area and dynamic convergence, jointly caused the local heavy rain and rainstorm weather. (2) The uplifting conditions of the heavy rainfall were the surface convergence line and meso-scale vortex on 700 hPa. (3) The invasion of cold air to the low vortex on 700 hPa triggered the rainstorm. (4) The heavy rainfall was directly linked to the merging and strengthening of meso-scale convective cloud clusters over Tibetan Plateau moving northward and local new convective clouds over eastern Hexi Corridor. (5) The westerly jets on 200 hPa were coupled with the southern and southeastern low level jets. On the one hand, the coupling strengthened the high-level divergence and ascending motion by pumping action. On the other hand, the convergence of southerly and southeasterly jets below 700 hPa with northwest wind triggered the unstable energy to release, and formed strong upward motion. Meanwhile, the southerly and southeasterly jets transported water vapor to northern Minqin of Gansu Province, and joined with local water vapor and strengthened.

Key words: heavy rainfall, large scale, meso-scale, jet

摘要:

针对2012年6月27日河西走廊东部突发性暴雨天气过程,利用Micaps常规资料、FY-2D卫星资料、NCEP再分析资料和82个区域气象站及6个自动气象站逐时降水资料,从天气特征、高低空急流、水汽条件、中尺度特征、稳定度、垂直运动等方面进行综合分析。结果表明:(1)此次暴雨的大尺度环流特征为典型的“北槽南涡”,即500 hPa贝加尔湖冷槽东移南压携带冷空气从柴达木低涡后部侵入与其汇合,冷暖空气在河西走廊中东部交汇。同时鞍型场的稳定维持,为柴达木低涡的发生发展提供背景,进一步加强了低空锋区和动力辐合,造成本地大到暴雨及暴雨天气;(2)700 hPa中尺度低涡和地面辐合线为此次暴雨提供了抬升条件;(3)冷空气侵入700 hPa低涡成为此次暴雨的触发机制;(4)高原中尺度对流云团发展北上与河西走廊东部新生对流云团合并加强是造成大到暴雨的直接原因;(5)高空西风急流与中低空偏南和东南急流的耦合,中层干冷、低层暖湿,环境风垂直切变以及散度“上正下负”和涡度“上负下正”的强上升运动区都为大降水提供了有利条件。

关键词: 突发性暴雨, 大尺度, 中尺度, 急流

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