盛夏一次大暴雨过程成因分析

Cause Analysis of a Heavy Rain in Midsummer

利用常规高空、地面观测资料以及FY-2E卫星云图等资料,对2017年8月19—20日发生在陕西省商南县青山镇的大暴雨天气过程进行综合分析。结果表明,东路冷空气和副高是此次暴雨的主要影响系统;副高外围的西南暖湿气流、西南涡东北侧切变后西北干冷气流和山东半岛低涡后东路回流湿冷气流这3股气流在商洛上空的交汇,为此次大暴雨过程提供了充沛的水汽和能量;暴雨区上空垂直运动发展旺盛且深厚,为大暴雨提供了抬升条件;高空急流右侧的强辐散为大暴雨上升运动和深对流形成提供了重要条件。双重辐合-辐散产生的强烈上升运动,抽吸作用明显,为深对流的发展提供了条件,也促进了大暴雨区附近小尺度系统的产生和维持。喇叭口地形触发了γ尺度对流云团的生成和发展,3个γ尺度对流系统的发展,造成2次强降水叠加形成此次大暴雨天气过程。

Based on the conventional high altitude and ground observation data and FY2E satellite cloud map,the heavy rain process in Qingshan Town of Shaanxi Province from August 19 to 20,2017 was analyzed.The results showed that the cold air and subtropical high in the east were the main influence systems of the rainstorm.The southwest warm and humid air flow around the subtropical high,the northwest dry and cold air flow after the shear in the northeast of the southwest vortex and the return wet and cold air flow in the east of the low vortex in Shandong Peninsula intersected over Shangluo,which provided abundant water vapor and energy for the heavy rain process.The vertical motion over the rainstorm area was vigorous and deep,which provided the lifting condition for the rainstorm.The strong divergence on the right side of the upper jet provided important conditions for the upwelling and deep convection of heavy rain.The strong upward motion of double convergence and divergence,with obvious suction effect,provided conditions for the development of deep convection and promoted the generation and maintenance of smallscale system near the heavy rainfall area.The formation and development of theγscale convective cloud clusters and the development of threeγscale convective systems were triggered by the bellmouth topography,which resulted in the formation of the torrential rain process by the superposition of two heavy rainfall events.