| 四川盆地“8.11”暴雨过程中低空急流作用分析 |
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| 引用本文： | 周懿,青逸雨,郭云云,代昕鹭.四川盆地“8.11”暴雨过程中低空急流作用分析[J].高原山地气象研究,2022,42(1):51-60. |
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| 作者姓名： | 周懿 青逸雨 郭云云 代昕鹭 |
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| 作者单位： | 1.四川省气象台, 成都 610072 |
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| 基金项目： | 高原与盆地暴雨旱涝灾害四川省重点实验室青年专项（SCQXKJQN2020023，省重实验室2018-青年-03） |
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| 摘 要： | 利用高空探测、地面加密区域自动气象站、NCEP1°×1°再分析、FY-4A红外云图、多普勒天气雷达和风廓线雷达等资料，分析了2020年8月11~13日四川盆地一次区域性暴雨过程的降水时空分布、环流背景和风暴系统演变等特征，并重点探讨了低空急流在此次过程中的作用。结果表明:（1）此次过程发生在“东高西低”的环流背景下，主要影响因子为500 hPa低槽、副高和西南涡。（2）低空急流的出现有利于正涡度柱的形成和上升气流支的建立，盆地西北部地形作用可以使上升辐合增强。（3）低空急流为暴雨区带来水汽和不稳定能量。（4）急流对降水风暴系统的影响主要分两个阶段。第一阶段以东南急流为主导，一方面引导对流系统向西北方向移动和增强，一方面在四川盆地西北部山前激发强对流回波带。第二阶段以西南涡西北象限的东北急流为主导，一方面在急流出口左侧形成强动力辐合，一方面将低涡南部的暖湿空气向MCS输送。整个影响过程中，急流主体下边界由3000 m下降到600 m，主导风向由东南风转为西北风。（5）低空急流增强时，MCS维持在代表站上游地区，呈准静止后向传播特征；低空急流减弱时，MCS的准静止状态被打破，对流系统迅速移向代表站，带来短时强降水。（6）龙泉山脉使近地层东北急流气旋性弯曲增大，水平辐合增强。当MCS经过时，龙泉山为地形辐合带，激发新生单体在山麓西侧形成并沿山脉向东北方向移动。
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| 关 键 词： | 低空急流 暴雨 MCS |
| 收稿时间： | 2021-08-11 |
Analysis on Low-level Jet Stream of the '8.11' Rainstorm in Sichuan |
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| Affiliation: | 1.Sichuan Provincial Meteorological Observatory, Chengdu 610072, China2.Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province, Chengdu 610072, China3.Nanjing University of Information Science and Technology, Nanjing 210044, China |
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| Abstract: | Using high altitude detection data, ground encryption regional automatic weather station data, NCEP1°×1°reanalysis data and FY-4A infrared cloud image data, Doppler weather radar data and wind profile radar data, the temporal and spatial distribution of precipitation, circulation background and storm system evolution of a regional rainstorm process in Sichuan Basin from 11 to 13 August 2020 were analyzed, and the role of low-altitude jet in this process was discussed. The results show that: (1) This process occurred in the background of 'east-high-pressure and west-low-pressure', the main influencing factors were 500hPa low trough, subtropical high and southwest vortex. (2) The emergence of low-level jet was conducive to the formation of positive vorticity column and the establishment of upflow branch, and the topographic action in the northwest of the basin enhanced the upward convergence. (3) Low level jet brought water vapor and unstable energy to the rainstorm area. (4) The influence of jet on precipitation storm system could be divided into two stages. The first stage was dominated by southeast jet. On the one hand, it led the convective system to move and strengthen in the northwest direction, and on the other hand, it triggered the strong convective echo zone in the northwest of Sichuan Basin. The second stage was dominated by the northeast jet in the northwest quadrant of the southwest vortex. On the one hand, strong dynamic convergence was formed on the left side of the jet outlet, and on the other hand, warm and humid air in the south of the vortex was transported to MCS. During the whole influence process, the lower boundary of the main body of the jet stream decreased from 3000m to 600m, and the dominant wind direction changed from southeast to northwest. (5) When the low-level jet intensified, MCS was maintained in the upstream area of the representative station, showing the characteristics of quasi-static backward propagation. When the low-level jet stream weakened, the quasi-static state of MCS was broken, and the convective system moved quickly to the representative station, bringing short-term heavy precipitation. (6) The Longquan Mountain increased the cyclonic angle of the northeast jet stream in the surface layer and enhanced the horizontal convergence. When MCS passed over Longquan Mountain, it was a topographic convergence zone, and the new cells were excited to form on the west side of the piedmont and move northeast along the mountain. |
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