重庆“6·8”大暴雨过程诊断分析
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摘要
该文利用NCEP再分析资料和地面观测资料,针对2017年6月8日20时—10日20时重庆地区出现的一次大暴雨过程,对过程发生前的降水实况、环流形势、对流潜势、能量条件、水汽条件、垂直运动以及对应过程发生发展最强时段的卫星及雷达特征进行了分析。此次过程为中高纬呈"两槽一脊"环流背景下,有长波槽分裂小槽东移,配合低层低涡系统及切变线的生成与发展,重庆位于副高584线附近,处在高空急流入口区右侧、低空急流左前侧的强抬升运动区。降水过程分为两个阶段,前一阶段为暖区降水,伴有较强的对流性特征,第二阶段伴随着冷空气的南压,冷暖空气在重庆长江沿线一带交绥,为混合性降水。第一阶段云图上呈现出暴雨云团形态,呈圆形、边界光滑、云团中心白亮区域对应降水大值区。雷达回波表现出较显著的低质心暖云降水特征,降水最强时段径向速度图上存在着明显的气旋式辐合区。第二阶段配合北方冷空气的侵入,云系呈带状分布和发展,伴随着对流云团的不断新生、合并、扩大,云团生命史较长,对应降水时间较长。雷达回波表现为层状云降水回波特征,且在重庆永川及周边区域存在"列车效应",从而造成了相应地区较长时间的持续性强降水。
Based on the NCEP reanalysis data and ground observation data, the process of a heavy rain occurred in Chongqing at 20:00 from June 8, 2017 to June 10, 2017 was analyzed from factors such as the circulation situation, the convective potential, the energy condition, the water vapor condition and the vertical motion before the heavy precipitation process as well as the characteristics shown in satellite and radar imagery when the precipitation is at its strongest. In the middle-high latitudes, the circulation presents a two trough and one ridge pattern. The long wave slot splits eastward, with the formation and development of the low-level vortex system and the shear line. Chongqing is located around the 584 line of subtropical high, where the strong lifting movement area is on the right of the upper jet stream entrance area and on the left front of the low jet. The precipitation process is divided into two stages. The first stage is precipitation in the warm area, with strong convective characteristics and the second stage is mixed precipitation accompanied by the invasion of cold air, with the cold and warm air converging along the Yangtze River in Chongqing. In the first stage, the cloud chart shows the shape of round rainstorm clouds with characteristics of smooth boundary, and the lowest brightness temperature corresponding to the large precipitation area. The radar echo presents significant characteristics of low mass warm cloud precipitation while the radial velocity map for the strongest precipitation period shows an obvious cyclone convergence zone. In the second stage, when the cold air is intruded from the north, the pattern of zonal distribution and development is presented in the cloud system. When convective clouds continuously emerge, merge and expand, the longer the entire life history of cloud clusters is, the longer the precipitation. The radar echo is characterized by stratiform cloud precipitation echo. Furthermore, there is a "train effect" in Yongchuan and its surrounding areas in Chongqing, resulting in persistent heavy precipitation in the those areas.
Based on the NCEP reanalysis data and ground observation data, the process of a heavy rain occurred in Chongqing at 20:00 from June 8, 2017 to June 10, 2017 was analyzed from factors such as the circulation situation, the convective potential, the energy condition, the water vapor condition and the vertical motion before the heavy precipitation process as well as the characteristics shown in satellite and radar imagery when the precipitation is at its strongest. In the middle-high latitudes, the circulation presents a two trough and one ridge pattern. The long wave slot splits eastward, with the formation and development of the low-level vortex system and the shear line. Chongqing is located around the 584 line of subtropical high, where the strong lifting movement area is on the right of the upper jet stream entrance area and on the left front of the low jet. The precipitation process is divided into two stages. The first stage is precipitation in the warm area, with strong convective characteristics and the second stage is mixed precipitation accompanied by the invasion of cold air, with the cold and warm air converging along the Yangtze River in Chongqing. In the first stage, the cloud chart shows the shape of round rainstorm clouds with characteristics of smooth boundary, and the lowest brightness temperature corresponding to the large precipitation area. The radar echo presents significant characteristics of low mass warm cloud precipitation while the radial velocity map for the strongest precipitation period shows an obvious cyclone convergence zone. In the second stage, when the cold air is intruded from the north, the pattern of zonal distribution and development is presented in the cloud system. When convective clouds continuously emerge, merge and expand, the longer the entire life history of cloud clusters is, the longer the precipitation. The radar echo is characterized by stratiform cloud precipitation echo. Furthermore, there is a "train effect" in Yongchuan and its surrounding areas in Chongqing, resulting in persistent heavy precipitation in the those areas.
引文
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[3] Shen Yongping,Wang Guoya.Key findings and assessment results of IPCC WGI Fifth Assessment Report[J].Journal of Glaciology and Geocryology,2013,35(5):1 068-1 076.
[4] 卢萍,翟丹华,李英,等.影响重庆暴雨的三类西南低涡浅析[J].热带气象学报,2014,30(4):736-746.
[5] 石鹏翔,刘海文,段伯隆,等.影响重庆夏季暴雨的中尺度低涡的气候学特征[J].成都信息工程学院学报,2016,31(3):305-310.
[6] 张焱,白莹莹,唐晓萍.2009年6月重庆区域暴雨的成因分析[J].贵州气象,2013,37(3):25-29.
[7] 刘毅,王欢,牟容,等.重庆地区一次暴雨天气过程分析[J].高原山地气象研究,2009(s1):83-89.
[8] 翟丹华,刘跃晨,廖晓荔,等.重庆“7.21”暴雨天气过程的初步诊断分析[J].高原山地气象研究,2009(s1):53-59.
[9] 陈鹏,刘德,周盈颖,等.一次重庆特大暴雨过程的中尺度分析[J].高原气象,2015,34(1):82-92.
[10]王红丽,易俊莲.一次西南低涡诱发四川盆地持续性暴雨的诊断分析[J].贵州气象,2015,39(3):13-20.
[11]周毅,王中.一次典型盆地涡大暴雨过程的中尺度分析[J].贵州气象,2002,26(3):11-13.
[12]曾波,何光碧,余莲.川渝地区两类西南涡形成前环境物理量场分析[J].高原山地气象研究,2016,36(4):9-16.
[13]翟丹华,刘德,李强,等.引发重庆中西部暴雨的西南低涡特征分析[J].高原气象,2014,33(1):140-147.
[14]何光碧.西南低涡研究综述[J].气象,2012,38(2):155-163.