蒙古冷涡影响下的兰州连续强对流天气

利用常规气象观测资料、环流再分析资料,采用天气动力学诊断方法和强天气分析技术,对兰州市2015年7月连续11 d的强对流天气成因进行分析,针对致灾最重的7月13日雹暴天气进行大尺度环流背景、物理量场及中尺度分析;同时,将2013年8月连续5 d的强对流天气与2015年7月连续11 d的强对流天气进行天气实况、环流形势的对比分析。结果表明,夏季500 h Pa高空蒙古冷涡与新疆至青海一带的大陆高压相配合,使兰州地区处于冷涡西南部的西北气流控制下,从冷涡底部不断分裂下滑的冷槽,中高层冷槽和低层暖温度脊的上下叠置,有利于对流不稳定的建立和发展,极易造成兰州地区午后强对流天气。蒙古冷涡的位置及强度,决定了兰州地区连续性强对流天气的持续日数、对流性天气的强度及影响范围。

Continuous Strong Convective Weather under the Influence of Mongolian Cold Vortex in Lanzhou

Based on the conventional meteorological observation data and cyclic reanalysis data, the causes of strong convective weather in Lanzhou City in July 2015 were analyzed by weather dynamics diagnosis method and strong weather analysis technique,and a large-scale circu-lation background, physical field and mesoscale were analyzed for the most damaging hail storm weather on July 13.At the same time, the con-vective weather in August 2013 for 5 consecutive days was compared with the strong convective weather in July 2015 for 11 days from weather conditions, weather circulation situation.The results showed that the Mongolian cold vortex at 500 hPa in summer coincided with the continen-tal high pressure from Xinjiang area to Qinghai, so that the Lanzhou area was under the control of the northwest airflow in the southwest of the cold vortex.From the bottom of the cold vortex to continue to split down the cold trough, high-level cold trough and low-level warm ridge above and below the stack, were conducive to the establishment and development of convective instability, easily lead to strong convective weather in Lanzhou.The location and intensity of the Mongolian cold vortex determined the duration of continuous convective weather in Lanzhou, the in-tensity and influence of convective weather.