利用风廓线雷达高时空分辨率资料, 对2012年4月在广州出现两次暴雨期间低空流场的主要特征进行了分析。结果表明: (1)在暴雨发生前, 动量由高空迅速下传, 且不断增强, 使得强风速不断下传, 导致低空急流的建立及增强, 从而使得上下层垂直风切变增大, 正涡度环流加强, 为暴雨的产生提供了很好的动力条件, 当伴随有西南暖湿气流输送的水汽条件时, 触发了暴雨的产生; (2)低空急流指数I值的脉动与强降水的发生有密切关系, 在每次强降水发生前1~2 h I值都会迅速增大, 强降水发生后I值迅速减小; (3)低层风场垂直切变增强以及出现极值的时间与急流下传及出现极值的时间具有较好的时间、空间对应关系, 说明正是由于低空急流的下传、增强, 导致了风场垂直切变的增强, 且局部垂直风切变要比平均垂直风切变大得多。
By using the windprofiler data, this paper studies the relationship between mesoscale wind field changes and rainstorm. Firstly, it is indicated that the high spatial and temporal resolution data can clearly reveal the effect of mesoscale wind filed changes such as low-level jet and low-level wind shear before the heavy precipitation happens. Before the heavy precipitation happens, the strong wind field and the momentum continuously go downstream, making the low-level positive vorticity increase, with the warm and humid air, trigger the precipitation. Secondly, an index I is designed to represent the intensity and height of the low-level jet, the index will increase rapidly before the heavy precipitation. Thirdly, the low-level vertical wind shear increases significantly, and it plays a significant role in triggering the generation of heavy precipitation.
[1]黄治勇, 周志敏, 徐桂荣, 等. 风廓线雷达和地基微波辐射计在冰雹天气监测中的应用[J]. 高原气象, 2015, 34(1): 269-278, doi: 10.7522/j.issn.1000-0534.2013.00130.
[2]肖艳姣, 万玉发, 吴涛, 等. 基于多普勒天气雷达的两种垂直风廓线反演方法的对比分析[J]. 高原气象, 2015, 34(1): 288-297, doi: 10.7522/j.issn.1000-0534.2013.00136.
[3]Zhong Shiyuan, Fast J D, Bian Xindi. A case study of the great plains low-level jet using wind profiler network data and a high-resolution mesoscale model[J]. Mon Wea Rev, 1996, 124(5): 785-806.
[4]Peter T M, Jameson A R, Thomas D K, et al. A comparison between polarimetric radar and wind profiler observations of precipitation in tropical showers[J]. J Appl Meteor, 2001, 40(10): 1702-1717.
[5]Peter T M, Jameson A R, Thomas D K, et al. Combined wind profiler polarimetric radar studies of the vertical motion and microphysical characteristics of tropical sea-breeze thunder storms[J]. Mon Wea Rev, 2002, 130(9): 2228-2239.
[6]Gage K S, Nastrom G D. Relationship of precipitation to vertical motion observed directly by a VHF wind profiler during a spring upslope storm near Denver, Colorado[J]. Bull Meteor Amer Soc, 1985: 66(4): 394-397.
[7]Peter T M, Thomas D K. Evaluation of microphysical retrievals from polarimetric radar with wind profiler data[J]. J Appl Meteor, 2005, 44(6): 837-838.
[8]张京英, 漆梁波, 王庆华. 用雷达风廓线产品分析一次暴雨与高低空急流的关系[J]. 气象, 2003, 19(3): 285-290.
[9]陶诗言. 登陆我国台风研究概述[J]. 气象科学, 2005, 25(3): 319-329.
[10]刘淑媛, 郑永光, 陶祖钰. 利用风廓线雷达资料分析低空急流的脉动与暴雨关系[J]. 热带气象学报, 2005, 31(12): 41-44.
[11]吴启树, 郑颖青, 沈新勇, 等. 福建一次秋季大范围暴雨成因分析[J]. 气象科学, 2010, 30(1): 126-131.
[12]孙淑清, 翟国庆. 低空急流的不稳定性及其对暴雨的触发作用[J]. 大气科学, 1980, 4(4): 327-337.
[13]苗爱梅, 武捷, 赵海英, 等. 低空急流与山西大暴雨的统计关系及流型配置[J]. 高原气象, 2010, 29(4): 939-946.
[14]孙继松. 北京地区夏季边界层急流的基本特征及形成机理研究[J]. 大气科学, 2005, 29(3): 445-452.
[15]杨毅, 邱崇践. 利用多普勒雷达资料分析一次强降水的中尺度流场[J]. 高原气象, 2006, 25(5): 925-931.
[16]侯瑞钦, 程麟生. 网格嵌套技术对一次中尺度对流系统降水过程模拟的影响[J]. 高原气象, 2006, 25(3): 451-462.
[17]刘淑媛, 郑永光, 陶祖钰. 利用风廓线雷达资料分析低空急流的脉动与暴雨关系[J]. 热带气象学报, 2003, 19(3): 285-290.
[18]Rasmussen E N, Blanchard D O. A baseline climatology of sounding-derived supercell and tornado forecast parameters[J]. Wea Forecasting, 1998, 13(4): 1148-1164.
