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张文龙, 崔晓鹏, 黄荣. 复杂地形下北京雷暴新生地点变化的加密观测研究[J]. 大气科学, 2014, 38(5): 825-837. DOI: 10.3878/j.issn.1006-9895.1401.13102
引用本文: 张文龙, 崔晓鹏, 黄荣. 复杂地形下北京雷暴新生地点变化的加密观测研究[J]. 大气科学, 2014, 38(5): 825-837. DOI: 10.3878/j.issn.1006-9895.1401.13102
ZHANG Wenlong, CUI Xiaopeng, HUANG Rong. Intensive Observational Study on Evolution of Formation Location of Thunderstorms in Beijing under Complex Topographical Conditions[J]. Chinese Journal of Atmospheric Sciences, 2014, 38(5): 825-837. DOI: 10.3878/j.issn.1006-9895.1401.13102
Citation: ZHANG Wenlong, CUI Xiaopeng, HUANG Rong. Intensive Observational Study on Evolution of Formation Location of Thunderstorms in Beijing under Complex Topographical Conditions[J]. Chinese Journal of Atmospheric Sciences, 2014, 38(5): 825-837. DOI: 10.3878/j.issn.1006-9895.1401.13102

复杂地形下北京雷暴新生地点变化的加密观测研究

Intensive Observational Study on Evolution of Formation Location of Thunderstorms in Beijing under Complex Topographical Conditions

  • 摘要: 2008 年8 月14 日北京发生了雷暴群形式的局地暴雨,雷暴新生地点复杂多变,形成了多个γ 中尺度的强降水中心。本文利用近年来北京气象现代化建设取得的加密地面自动站、多普勒雷达、风廓线仪、微波辐射计等多种新型高时空分辨率观测资料及雷达四维变分同化系统(VDRAS)反演资料,通过精细分析地面(边界层)风场、温度场等的演变特征,讨论了雷暴新生地点变化的机制。结果表明:复杂地形与雷暴冷池出流作用相结合,主导了雷暴新生地点的变化,进而影响γ 中尺度强降水中心的变化;天气尺度高低空涡、槽的配合不一致,并且系统移动缓慢,以及对流层低层的弱的环境垂直风切变,是雷暴冷池结合复杂地形发挥雷暴新生地点主导作用的重要前提;复杂地形使得冷空气在一定范围内流动,在边界层产生碰撞和辐合,起到触发和增强对流作用,并使得对流风暴的形态和走向与地形呈现出紧密相关性;一定强度的冷池出流、边界层前期的暖湿空气和对流不稳定能量的积累,是冷池出流触发雷暴新生和演变的必要条件;北京周边地区的雷暴,通过其雷暴冷池出流沿着沟谷地形或向平原地区流动,与北京山谷或城区的边界层暖湿空气形成辐合抬升机制,触发雷暴新生。

     

    Abstract: A group of thunderstorms locally formed heavy rain in Beijing on August 14, 2008. The locations of the thunderstorms initiated were complex and variable, forming multiple γ-mesoscale heavy precipitation centers. Using high spatial and temporal resolution data obtained from the ground automatic weather stations, Doppler radar, wind profiler, and ground-based microwave radiometer, combined with the analysis data retrieved by the four dimensional variational Doppler radar analysis system (VDRAS), the characteristics of the ground (boundary layer) wind and temperature evolution are analyzed, and the mechanism of the location change of the newly formed thunderstorms are discussed in this paper. The following results are given: (1) The cold pool outflow of pre-existing thunderstorms combined with a complex terrain played a leading role in determining the location of newly formed thunderstorm, thereby affecting the location of γ-mesoscale heavy precipitation center. (2) The inconsistency between the synoptic scale vortex at upper levels and trough at lower levels, the slow movement of the synoptic scale systems, and weak environmental vertical wind shear in the lower troposphere combined to form an important precondition. (3) The complex terrain caused the cold air flow within a certain range, and the collision and convergence of these cold air in the boundary layer triggered and enhanced convection; thus, a close relationship is shown between the shapes of the convective storms and terrain. (4) A certain intensity of the cold pool flow, pre-existing warm and humid air in the boundary layer, and accumulation of convective instability energy were essential conditions for the cold pool outflow to trigger the new thunderstorm. (5) Finally, the cold pool outflows of thunderstorms around Beijing flowed along the valley terrain or to the plain of city, then formed a boundary convergent uplift mechanism with the warm and moist air, which subsequently triggered the thunderstorms.

     

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