双月刊

ISSN 1006-9895

CN 11-1768/O4

基于多雷达观测和数值模拟的中天山北坡夏季降水过程研究
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1.中国气象局气溶胶与云降水重点开放实验室/南京信息工程大学气象灾害预报预警与评估协同创新中心;2.中国气象局云雾物理环境重点开放实验室;3.新疆维吾尔自治区人工影响天气办公室

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科技部重点研发项目,西北人工影响天气工程项目,中国气象局西北区域人影建设研究试验项目,国家自然科学基金,江苏省自然科学基金


A Case Study of Summer Precipitation Process in the Central Tianshan Area using Multi-radar Observation and Model Simulation
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1.Key Laboratory for Aerosol–Cloud Precipitation of China Meteorological Administration,Nanjing University of Information Science Technology /Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters;2.Weather Modification Office of Xinjiang Uygur Autonomous Region,Xinjiang

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    摘要:

    基于微雨雷达、Ka波段云雷达、C波段天气雷达和微波辐射计等仪器的观测资料对2019年7月27日中天山地区一次地形云降水过程的精细结构及演变过程进行了分析,并结合WRF高分辨率数值模式模拟结果研究了此次过程的热力不稳定结构及风的垂直切变对云发展的影响。结果表明:此次降水过程中天山北坡区域受到地形热力作用,形成偏北方向的爬坡气流,并与翻越天山山脉的偏南气流辐合,在局部形成对流;雷达观测发现,由于天山山区受到高空西风的控制,局地产生的对流云团不足以突破中天山北坡上空的风速较大的西南气流或偏西气流,低层的偏北气流被高层气流夹带而转向形成风切变层。降水发生后,低层对流云团被限制在风切变层以下,云顶平整且高度较低,风切变层对对流云团存在明显的抑制作用。通过分析模式模拟结果,此次降水过程中风切变对中天山北坡降水云的发展及热力不稳定变化影响十分重要,高层西南风对相当位温的平流输送使得风切变层上空更倾向于热力不稳定,同时使其下方更倾向于热力稳定从而抑制低层对流而促进高层对流的发展。当低层对流云团强度不足以突破其上空因垂直风切变导致的稳定层结,对流便会被局限于垂直风切变层以下,使得降水强度减弱。

    Abstract:

    Measurements were conducted using a micro-rain radar, a Ka-band cloud radar and a microwave radiometer to analyze the fine vertical structure and evolution process in an orographic precipitation process in the middle Tianshan area. In addition, a high-resolution simulation is made to analyze the instability and its influence on the generation of the clouds. The observations show that the precipitation was generated due to the convergence between the southwesterly wind flew across the mountain ridge and the northernly wind that induced due to the thermal forcing by terrain. Because the observed convective updraft was not strong enough, the low-level northernly flow turned to the south as it approaching the high-level southwesterly wind, forming strong wind shear. After the precipitation occurred, the low-level convective clouds were confined below the windshear layer, and the cloud tops were generally flat and low, indicating the windshear layer has a significant inhibiting effect on the convection. The model simulation suggests the influence of the wind shear on the development of precipitation clouds and the change of thermal instability on the northern slope of the Central Tianshan Mountains during this precipitation is very important. The advective transport of considerable potential temperature by upper-level southerly winds made the upper layer above the wind shear layer more thermally unstable, and made the layer below it more thermally stable, thus suppressing low-level convection and promoting upper-level convection. If low-level convective updrafts were not strong enough to break through the stable laminar junction caused by vertical wind shear, convection will be confined below the vertical wind shear layer, preventing intense precipitation.

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  • 收稿日期:2021-10-20
  • 最后修改日期:2022-04-15
  • 录用日期:2022-06-29
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