| 2018年北京“7.16”暖区特大暴雨特征及形成机制研究 |
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| 引用本文： | 雷蕾,邢楠,周璇,孙继松,翟亮,荆浩,郭金兰.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,2020,78(1):1-17. |
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| 作者姓名： | 雷蕾 邢楠 周璇 孙继松 翟亮 荆浩 郭金兰 |
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| 作者单位： | 1.北京市气象台，北京，100089 |
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| 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）、国家自然科学基金项目（41575050、41475051）、中国气象局预报员专项（CMAYBY2018-001）、中央科研院所专项（IUMKY201606） |
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| 摘 要： | 利用京津冀区域加密自动气象站、SA多普勒天气雷达、L波段风廓线雷达、NCEP 0.25° 再分析资料及0.03° 高分辨率地形资料研究了北京2018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热带高压边缘的暖气团（θse高能区）中，无明显冷空气强迫，斜压性弱，有丰沛的水汽，850 hPa以下出现强水汽辐合。（2）暴雨的中尺度对流系统发展有3个过程:带状对流建立和局地强雨团影响、北京北部“列车效应”南部雷暴冷池出流造成对流加强和移动、平原地区线状对流重建。（3）暴雨发生前，低层西南风出现风速脉动，低空急流建立。首先在2500—3500 m高度形成低空急流，2 h后2500 m以下风速显著增大，5 h后急流厚度由边界层伸展到700 hPa。急流出口区降压，低层出现气旋性风场或切变，有利于垂直上升运动发展，触发和加强对流。（4）西南低空急流暖湿输送导致高温、高湿、高能的对流不稳定层结反复重建，这是对流发展加强的重要原因。（5）地面辐合线是对流触发并逐渐组织成带状对流系统的关键影响因素。地面辐合线方向、低空急流轴、回波移动方向三者几乎重叠是造成对流后向传播和“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。北京最大雨强≥40 mm/h站点中的77.4%位于西南部和东北部200—600 m海拔高度处。偏东风在华北西部太行山局地迎风坡触发对流，西南低空急流在北京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。
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| 关 键 词： | 暖区特大暴雨 低空急流 地面辐合线 列车效应 地形 |
| 收稿时间： | 2019/4/5 0:00:00 |
| 修稿时间： | 2019/8/14 0:00:00 |
A study on the warm-sector torrential rainfall during 15-16 July 2018 in Beijing area |
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| LEI Lei,XING Nan,ZHOU Xuan,SUN Jisong,ZHAI Liang,JING Hao and GUO Jinlan.A study on the warm-sector torrential rainfall during 15-16 July 2018 in Beijing area[J].Acta Meteorologica Sinica,2020,78(1):1-17. |
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| Authors: | LEI Lei XING Nan ZHOU Xuan SUN Jisong ZHAI Liang JING Hao and GUO Jinlan |
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| Institution: | 1.Beijing Municipal Weather Forecast Center，Beijing 100089，China2.State Key Laboratory of Severe Weather，Chinese Academy of Meteorology Sciences，Beijing 100081，China |
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| Abstract: | The characteristics and formation mechanism of a warm-sector torrential rainfall event in Beijing area during 15—16 July 2018 are analyzed using observations from regional automatic weather stations, SA Doppler weather radar, L-band Wind Profile radar, the NCEP 0.25° reanalysis product and high-resolution (0.03°) terrain data. Results are as follows: (1) The torrential rain occurred within the warm air mass (high θse energy zone) on the edge of the sub-tropical high, while there was no significant cold air forcing and the baroclinicity was weak. Specific humidity was high and strong low-level water vapor convergence occurred below 850 hPa. (2) The meso-scale convection experienced three development and evolution stages during the torrential rain process. The first stage corresponded to convective band formation and local rainfall strengthening. The second was the mature and strengthening stage, when the "echo training" developed in the north and the cold pool and gust front in the south resulted in the intensification and moving of convection. In the third stage, the line-shaped convective system established. (3) Before the occurrence of the warm-sector torrential rain, southwesterly winds in the lower layer fluctuated and the low-level jet (LLJ) was established. The wind speed first increased at 2500—3500 m, and significant increase occurred at 2500 m 2 h later. 5 h later, the LLJ reached 700 hPa. The low-level pressure decreased in the outlet area of the LLJ, while cyclonic circulation and wind shear developed, which was conducive to ascending motion and triggered/strengthened convective activities. (4) The warm and moist air mass transport by the LLJ led to repetitive formation of low-level convective instability with high temperature, high humidity and high energy. This was an important reason for the generation and combination of convective cells, the formation of belt-shaped convection, and the rapid reconstruction of the line-shaped convection. (5) Convergence in the surface was an important factor that triggered convective cells, which gradually formed belt-shaped convection. The direction of the surface convergence line, the LLJ axis and the moving direction of echoes were almost the same, which was favorable for backward propagation of the thunderstorm and the formation of "echo training" along the convective belt. (6) The Taihang Mountain and Yan Mountain had important effects on convection triggering and heavy rainfall development. 77.4% of the stations with the heaviest rain reaching or exceeding 40 mm/h were located at altitudes of 200—600 m in the southwestern and northeastern mountainous areas. The easterly wind triggered convection on the windward slope in the west, while the southwesterly LLJ was more significant along the windward slope and the horn-shaped topography in the north, resulting in heavy rain. |
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| Keywords: | Warm sector torrential rain Low-level jets Ground surface convergence line Echo training Terrain |
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