| 摘要: |
| 该文利用常规气象观测资料及NCEP 1°×1°再分析资料，对2018年4月12日08时—13日08时蒙古气旋与西南涡协同作用下，陕西省出现大范围降水，陕南局地暴雨的形成机理进行诊断分析。结果表明：（1）乌拉尔山高脊与贝加尔湖高脊之间的蒙古低槽东移发展为蒙古冷涡，地面冷锋移入低压，形成蒙古气旋。青藏高原东侧生成的西南涡与蒙古冷涡接近同位相，西南涡前侧高温高湿的偏南气流向北输送到陕西北部，蒙古冷涡底部干冷空气南下到陕西南部。蒙古冷涡与西南涡的协同作用下，蒙古冷涡南部与西南涡北部形成2条切变线及地面冷锋过境是陕西省降水的主要影响系统。（2）锋生阶段暖区一侧θse受西南涡偏南暖湿气流的输送得到增大，锋区两侧能量差变大，由于两涡输送冷暖气流的持续作用，锋区移动缓慢，上升运动加强，降水范围广、持续时间长。（3）蒙古冷涡是不对称的冷性低涡，西南涡是暖性低涡，2个不同冷暖特性低值系统同位相具有协同作用的机制，蒙古冷涡底部冷空气南下侵入西南涡，增大了西南涡的气旋性涡度。西南涡增强后，向北持续输送暖湿气流到陕北地区，蒙古冷涡底部冷空气南下影响西南涡北侧切变线稳定少动是陕南暴雨的成因。 |
| 关键词: 暴雨；蒙古气旋；西南涡；锋生 |
| DOI： |
| 投稿时间：2022-12-03 |
| 基金项目:中国气象局预报员专项（CMAYBY2018-076）； 榆林市科学技术局技术研发专项（YF-2021-025) 资助 |
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| Analysis on the Cause of a Spring Rainstorm under the Joint Action of Mongolian Cyclone and Southwest Vortex |
| LIU Huimin,BAI Yue,ZHANG Jiankang,MA Xiaohua,XI Zuolian |
| (Yulin Meteorological Bureau of Shaanxi Province, Yulin 719000 , China;Western Airport Group Yulin Limited Company, Yulin 719000 , China;Meteorological Observatory of Shaanxi Province, Xi'an 710014 ,China;Guiyang Meteorological Bureau of Guizhou Province, Guiyang 550002 ,China) |
| Abstract: |
| Based on meteorological data and NCEP 1°×1° reanalysis data, a large-scale precipitation and local heavy rain weather process in Shaanxi Province under the interaction of Mongolian cyclone and Plateau vortex during April 12-13, 2018 was diagnosed and analyzed. The results show that:（1） the Mongolian cold developed and formed from the Mongolian low trough between the Ural ridge and Baikal ridge, with the surface cold front moving into the low-vortex pressure, forming the Mongolian cyclone. At the same time, the Southwest vortex generated in the east of the plateau is close to the same phase as the Mongolian cyclone, which is conducive to the northward transport of the southerly air with high temperature and humidity in front of the low vortex to northem shaanxi,while the dry and cold air at the bottom of the Mongolian cold vortex flows southward to southern Shaanxi.Under the synergistic effect of the Mongolian cold vortex and the Southwest vortex, two shear lines are formed in the southern part of the Mongolian cold vortex and the northern part of the Southwest vortex, and the passage of the surface cold front is the main influencing system of precipitation in Shaanxi Province. （2） In the fronto genesis stage of the cold front, θse on the side of the warm area is increased by the southward warm and moist air of the southwest vortex, and the energy difference between the two sides of the front area becomes larger. Due to the continuous action of the cold and warm air transported by the two vortices, the front area moves slowly, the upward movement is strengthened, and the precipitation range is wide and the duration is long. （3） The Mongolia cold vortex is an asymmetric cold low vortex, while the southwest vortex is a warm low vortex. These two low value systems with different cold and warm characteristics have a synergistic mechanism in the same phase. The cold air at the bottom of the Mongolia cold vortex intrudes southward into the southwest vortex, which increases the cyclonic vorticity of the southwest vortex. After the strengthening of the southwest vortex, the warm and wet air continued to be transported northward to the Shaanxi North area. The cold air at the bottom of the Mongolia cold vortex moved southward on the north side of the southwest vortex and formed the shear line stable and less moving, which was the cause of the heavy rain in southern Shaanxi. |
| Key words: rainstorm；Mongolia cyclone；southwest vortex；front |
