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长江流域一次大暴雨过程的低空急流形成和影响机制分析
吴哲珺1,2, 包云轩1,2, 朱霆3, 葛晶晶3
1. 南京信息工程大学气象灾害预报和评估协同创新中心,江苏 南京 210044;2. 中国气象局交通气象重点开放实验室/ 江苏省气象科学研究所,江苏 南京 210009;3. 中国人民解放军31110部队气象局,江苏 南京 210016
摘要:
利用WRF模式对2016年6月30日—7月6日长江流域的一次大暴雨天气过程中的低空急流进行数值模拟,在成功模拟低空急流基础上,分析此次急流过程中可能的影响机制;同时对地形高度进行敏感性试验,分析地形因素对此次低空急流可能的影响。(1) 此次低空急流发生时,东侧为西太平洋副热带高压,西侧则为西南涡。这种“东高西低”的高低压配置为低空急流的形成与发展提供了有利的背景场。(2) 高空急流和低空急流的耦合作用是低空急流发展的一个重要背景条件。(3) 垂直方向高空动量不断下传为低空系统的发展提供了动力支持,是低空急流发生的一个重要条件。(4) 逆温和垂直风切变之间的正反馈机制是低空急流形成与加强的因素之一。(5) 山体在急流生成及发展过程中对气流有摩擦和阻挡作用,这种阻挡作用随着山体地形高度的增加而有所加强,同时山脉的走向会改变原始的风向,使得急流前端超前或滞后。青藏高原有强背风波效应,它的绕流和挤压作用会使得低空气流表现为狭长的带状,使动量更加聚集从而风速增加形成低空急流。
关键词:  暴雨  低空急流  数值模拟  机制分析  地形  敏感性试验
DOI:10.16032/j.issn.1004-4965.2019.038
分类号:
基金项目:
STUDY ON THE MECHANISM OF LOW-LEVEL JET IN A HEAVY RAINFALL IN THE YANGTZE RIVER BASIN
WU Zhe-jun1,2, BAO Yun-xuan1,2, ZHU Ting3, GE Jing-jing3
1. Collaborative Innovation Center on Forecast Meteorological Disaster Warning and Assessment, Nanjing University of Information Science and Technology, Nanjing 210044, China.;2. Key Laboratory of Transportation Meteorology, Jiangsu Meteorological Institute, Nanjing 210009, China.;3. Meteorological Office in 31110 Troops of Chinese People's Liberation Army, Nanjing 210016, China
Abstract:
The Weather Research and Forecast (WRF) model is used to simulate the low-level jet (LLJ) during a heavy rainfall process that occurred in Yangtze River valley from 30th June to 6th July 2016. Based on the successful simulation of LLJ, the possible mechanism of LLJ was analyzed. Meanwhile, a sensitivity test of the terrain height was performed to analyze the effect of topographic factors on the LLJ. The results are showed as follows: (1) This LLJ occurred with the western Pacific subtropical high in the east and the southwest vortex in the west. The situation of "east high and west low in the pressure field" provides a favorable background for the formation and development of LLJs. (2) The coupling of high-level jets and LLJs is an important background condition for the development of LLJ. (3) Constant vertical momentum downward from high-altitude provides momentum for LLJ, which is also an important condition for the occurrence of LLJ. (4) Positive feedback between temperature inversion and vertical wind shear is one of the factors that strengthen LLJ. (5) The mountain body has friction and blocking effect during the formation and development of LLJ which increases with the mountain height. Meanwhile, the direction of the mountains will change the original wind direction, making LLJ leading or lagging. Tibetan Plateau has strong lee wave effect, its flow and squeezing effects will make the air flow appear as a narrow band, which will accumulate the momentum and increase the air speed to form a low-level jet stream.
Key words:  rainstorm  low-level jet(LLJ)  numerical simulation  mechanism analysis  terrain  sensitivity test
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