doi:  10.3878/j.issn.1006-9895.1707.16238
雷暴大风过程中对流层中低层动量通量和动能通量输送特征研究

Analysis of Middle-level Momentum Flux and Kinetic Energy Flux in a Thunderstorm Event
摘要点击 1241  全文点击 183  投稿时间:2016-09-27  修订日期:2017-07-13
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基金:  中科院重点部署项目(KZZD-EW-05),北京自然基金项目(8142035),国家重点基础研究发展计划(2013CB430105),国家自然科学基金项目(41175060)
中文关键词:  雷暴大风 动量通量 动量下传 水平质量权重动能
英文关键词:  thunderstorm, meridional momentum, mass kinetic energy, downward transportation
     
作者中文名作者英文名单位
张琳娜Zhang Lin na北京市气象台
冉令坤RAN Ling kun中国科学院大气物理研究所
引用:张琳娜,冉令坤.2018.雷暴大风过程中对流层中低层动量通量和动能通量输送特征研究[J].大气科学
Citation:Zhang Lin na,RAN Ling kun.2018.Analysis of Middle-level Momentum Flux and Kinetic Energy Flux in a Thunderstorm Event[J].Chinese Journal of Atmospheric Sciences (in Chinese)
中文摘要:
      雷暴大风是一种灾害性强对流天气,雷暴大风的产生机理和预报方法研究一直以来主要集中在垂直风切变和对流指数等方面,对动量和动能输送方面的研究相对较少。北京发生过多次雷暴大风事件,一个典型特点是北京上游中低层存在大风速区,有动量下传加强地面大风的可能性。为了分析雷暴过程中地面大风的可能成因,对2014年5月31日北京地区一次范围广、强度大的雷暴大风过程进行高分辨率数值模拟,在成功模拟再现此次过程初生、发展、北移等演变过程的基础上,对经向动量和水平质量权重动能方程进行收支计算分析,研究引起地面大风(利用经向动量和水平动能来描述)的可能原因,进一步分析经向动量和水平质量权重动能的通量输送特征。研究结果表明,在近地面,经向动量和水平质量权重动能的通量散度是影响经向通量和水平质量权重动能局地变化的最重要强迫项。在对流层中下层,雷暴系统层云区后部入流和对流云区下沉气流把中低层的动量和动能向下传输,先后与近地面动量和动能的水平通量输送相汇合,一起向对流云区前沿输送;在北京西北部地形的阻挡抬升作用下,经向动量和动能的通量在对流云区前端近地面层辐合,产生较强的地面大风。 在近地面,经向动量和水平质量权重动能的垂直通量散度比水平通量散度要弱,但雷暴系统层云区中层入流和对流云区低层下沉气流是对流系统的典型环流结构,必然引起动量和动能下传,对近地面动量和动能的局地变化有一定贡献,对地面大风的促进作用是不能忽视的。总之,对流层中下层动量和动能的通量下传以及近地面水平通量传输对雷暴大风的发生发展有重要影响,在实际预报中需要给予特别关注。
Abstract:
      Thunderstorm is a kind of severe convections resulting in weather disaster. Its formation mechanism and forecast is an important subject. Generally, thunderstorm is characterized by middle-level large speed in upstream region. The descending flow in thunderstorm can transport downwards the middle-level momentum to strengthen the surface wind speed. In order to analyze possible cause of thunderstorm surface gale, a high resolution numerical simulation of a severe thunderstorm occurring in Beijing on 31 May 2014 was carried out. On the basis of successful simulation, the budget of meridional momentum and mass weighted horizontal kinetic energy was investigated. The flux transportation of meridional momentum and mass kinetic energy was examined. It was shown that the local changes of meridional momentum and mass kinetic energy near surface were primarily dominated by the divergence of meridional momentum and mass kinetic energy fluxes. In the middle and lower troposphere, the rear inflow in stratiform zone and descending flow in convective zone transported downwards meridional momentum and mass kinetic energy, and combined with the horizontal fluxes of meridional momentum and mass kinetic energy near surface. Then, the combining fluxes horizontally transported the meridional momentum and mass kinetic energy to the front of convective zone. Blocked by the terrain in northwest of Beijing, the combining flux converged in the front, and intensified the wind gust on the ground. The vertical flux divergence of meridional momentum and mass kinetic energy is weaker than the horizontal flux divergence near the surface. The middle-level rear inflow in stratiform zone and descending flow in convective zone were the typical vertical structure of thunderstorm. They necessarily resulted in the downward transportation of momentum and kinetic energy and made a certain contribution to the local changes of momentum and kinetic energy on the ground. In a world, the downward transportation of middle and lower-level momentum and kenitic energy in the troposphere plays an important role in development of thunderstorm. In the forecasting operation, the transportation of momentum and kinetic energy deserved special attention.
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