雷蕾,邢楠,周璇,孙继松. 2020. 2018年北京“7.16”暖区特大暴雨特征及形成机制研究[J]. 气象学报, ():-, doi:10.11676/qxxb2020.001
2018年北京“7.16”暖区特大暴雨特征及形成机制研究
Study on the warm sector torrential rain from 15 to 16 July 2018 in the Beijing area
投稿时间:2019-04-05  修订日期:2019-08-01
DOI:10.11676/qxxb2020.001
中文关键词:  暖区特大暴雨,低空急流,地面辐合线,列车效应,地形
英文关键词:warm sector torrential rain, LLJs, ground surface convergence line, echo training, terrain
基金项目:国家科技支撑计划课题(2015BAC03B04);公益性行业(气象)科研专项(GYHY201506006);中国气象局预报员专项(CMAYBY2018-001);国家自然科学基金;中央科研院所专项(IUMKY201606)
作者单位E-mail
雷蕾 北京市气象台 Leilei_bjt@126.com 
邢楠 北京市气象台 nxing0923@163.com 
周璇 北京市气象台 zhouxuan07@126.com 
孙继松 中国气象科学研究院灾害天气国家重点实验室 sunjs@cma.gov.cn 
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中文摘要:
      本文利用京津冀区域加密自动站、SA多普勒天气雷达、L波段风廓线雷达、NCEP0.25°再分析及0.03°高分辨率地形等资料综合分析了北京2018年7月15-16日暖区特大暴雨特征和形成机制。结果表明:(1)这次暖区特大暴雨发生在副高边缘的暖气团(θ_se高能区)中,无明显冷空气强迫,斜压性弱。副高外围有丰沛的水汽,850hPa以下出现强水汽辐合。(2)暴雨中尺度对流系统发展有三个过程:带状对流建立和局地强雨团影响、北部“列车效应”,南部雷暴冷池出流造成对流加强和移动、线状对流的重建。(3)出现暖区特大暴雨的动力条件:低层西南风出现风速脉动,低空急流建立。首先在2500-3500m加强为低空急流,2小时后2500m以下风速显著增大,5小时后急流厚度达到700hPa以下。急流出口区低层减压,出现气旋性风场或切变,有利于低层垂直上升运动发展,触发和加强对流。(4)西南低空急流暖湿输送作用表现为低层高温、高湿、高能的对流不稳定层结的建立和反复构建。这是对流单体生成和合并、带状对流形成、线状对流再次快速重建的重要原因。(5)地面辐合线是触发对流、并逐渐组织化形成带状对流系统的关键因素。地面辐合线走向、低空急流轴与回波移动方向三者几乎一致,是对流后向传播和“列车效应”的有利条件。(6)太行山和燕山地形对对流触发和暴雨增幅有重要影响。这次暴雨中最大雨强达到并超过40毫米/小时以上的站点中77.4%位于西南部和东北部海拔高度200-600m处。偏东风在西部迎风坡触发对流,西南低空急流在北部迎风坡和喇叭口地形处辐合和抬升更为显著,造成局地特大暴雨。
英文摘要:
      The characteristics and formation mechanism in a warm sector torrential rain in Beijing area from 15 to 16 July 2018 were analyzed by using the data of regional automatic weather station data, SA Doppler weather radar, L-band Wind Profile radar, NCEP 0.25° re-analysis and high-resolution (0.03°) terrain data. Results show that (1) the torrential rain occurred in the warm air mass (high θse energy zone) on the edge of sub-tropical high, with no significant cold air forcing and weak baroclinic air. It had high specific humidity, very large precipitation water and strong low-level vapor convergence below 850hPa. (2) Meso-scale convection in the torrential rain process had three development and evolution stages. First was convective band construction and local rainfall strengthening, second was maturity and strengthening phase with “echo training” in the north and thunder cold pool and gust pushing in the south area, third was the line convective system rebuilt. (3) The dynamic conditions in the warm torrential rain were that wind speed pulsation occurred in the south-west wind of the lower layer and the low-level jets (LLJs) was established. Wind speed firstly strengthened at 2500-3500m, two hours later, 2500m significantly increased, and 5 hours later, the LLJs reached 700hPa below. The low-level pressure decreased in the outlet area of LLJs and cyclone wind field or shear appeared which were conducive to the development of vertical rise movement and triggered and strengthened the convection. (4) The warm and humid transportation of LLJs was useful for the establishment and rebuilds of low-level convective unstable levels with high temperature, high humidity and high energy. This was an important reason for the generation and combination of cells, the formation of belt-shaped convection, and the rapid reconstruction of linear convection. (5) The ground convergence line was an important factor that triggered cells and gradually formed belt-shaped convection. The direction of the ground convergence line, the low-altitude rapids axis and the echo movement were almost the same, which was the favorable condition for the post-thunderstorm propagation and the "echo training" in the convection belt. (6) Tai-hang and Yan Mountain had important effects on convection triggering and heavy rainfall growth. 77.4% of the sites with the heaviest rains reaching and exceeding 40 mm/h were at altitudes of 200-600m in the southwest and northeast mountain areas. Easterly flows triggered convection on the west wind-forward slope, and the southwest LLJs were more significant in the northern wind-forward slope and the horn topography, resulting in heavy rain.
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