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陕西2次相似天气系统下强降雨差异的成因诊断

李明1高维英2 赵强1   

  1. 1.陕西省气象台,陕西西安710015;2.陕西省气象学会,陕西西安710016
  • 出版日期:2015-06-30 发布日期:2015-06-30
  • 作者简介:李明(1974-),男,硕士,高级工程师,主要从事天气预报及研究工作. E-mail:lm0223@sina.cn
  • 基金资助:

    中国气象局2014年气象关键技术集成与应用项目“陕西对流性强降雨预报技术集成与应用”(CMAGJ2014M52)、陕西省气象局研究型业务重点科研项目“产生短时大暴雨的中小尺度系统发生发展指标研究”(2013Z-3)及“陕西雷雨大风与冰雹强天气多尺度预报模型研究”(2015Z-2)共同资助

Diagnostic Analysis About Precipitation Difference Reasons of Two Heavy Rainfall Processes Under the Similar Synoptic Systems in Shaanxi Province

LI Ming1GAO Weiying2ZHAO Qiang1   

  1. 1. Shaanxi Meteorological Observatory, Xi’an 710015, China;2. Shaanxi Meteorological Society, Xi’an 710016, China
  • Online:2015-06-30 Published:2015-06-30

摘要:

利用常规观测资料、1°×1°NCEP再分析资料、自动站资料,从水汽、动力、不稳定条件方面,采用诊断分析方法对2011年7月28日(简称过程Ⅰ)关中西部、陕南西部区域性强降雨和2013年7月25日(简称过程Ⅱ)陕北南部分散性强降雨进行对比分析。结果表明:2次过程前期天气状况、环流形势、影响系统类似,但降雨差异大。过程Ⅰ低层切变线和辐合线明显,过程Ⅱ则弱;地面上,过程Ⅰ强降雨区处在高、低压之间的气压梯度密集带上,过程Ⅱ强降雨区则处于均压场中;过程Ⅰ强降雨区中低层比湿呈单峰型变化,水汽通量辐合强度大且深厚,有强烈水汽输入,过程Ⅱ强降雨区中低层比湿基本无变化,水汽通量辐合强度弱且浅薄,水汽输入弱;过程Ⅰ强降雨区中、低层有明显冷空气作用产生系统性强降雨,过程Ⅱ强降雨区仅在近地层有浅薄的弱冷空气扰动,在西南气流中激发湿对流;过程Ⅰ强降雨区低层对流不稳定、中高层为条件对称不稳定的混合型大气层结,而过程Ⅱ强降雨期间中层、低层大气均为对流不稳定层结。

 

关键词:
强降雨,
差异成因, 水汽, 冷空气, 不稳定

Abstract:

The synoptic systems and conditions of water vapor, dynamic, instability about a regional heavy rainfall occuring in west parts of Guanzhong and south Shaanxi on 28 July 2011( process I) and a dispersive heavy rainfall in south part of north Shaanxi on 25 July 2013(process II) were diagnosed based on conventional observation data, NCEP reanalysis data with 1°×1° spatial resolution and automatic weather station data. The results show that the weather conditions, circulation situations and synoptic influential systems of the two processes were similar but precipitation difference between them was obvious. The low-level wind shear and convergence line of the process I was obvious , but that of the process II was weak. The rainfall area of the process I was located in the intensive belt of pressure gradient between surface high pressure and low pressure, while that of the process II was in uniform pressure field. The specific humidity of the mid-low level atmosphere over heavy rainfall area presented single-peak change and there was deep and strong water vapor flux convergence and drastic water vapor inflow  during the process I, while specific humidity of the mid-low level atmosphere over heavy rainfall area was almost no change and there was shallow and weak water vapor flux convergence, slight water vapor inflow during the process II. The influence of obvious cold air of the mid-low level atmosphere resulting in heavy rainfall of the process I, while there was only the shallow cold air over surface layer which excited moist convection in the southwest air current over the rainfall area of the process II. During the process I, the atmosphere over the heavy rainfall area was mixed-type instability stratification with convective instability in low level and conditional symmetric instability in mid-high level, while the mid-low level atmosphere over rainfall area during the process  II was only convective instability stratification.

 

Key words: heavy rainfall, reasons of precipitation difference, water vapor, cold air, instability

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