渤海北部东岸海风锋活动及其触发对流特征分析

Characteristics of sea breeze fronts and triggered convection on the eastern coast of the northern Bohai Sea

利用常规观测、雷达、卫星及加密自动气象站等资料,对2015年、2018年和2019年渤海北部东岸海风锋活动及其触发的对流特征进行统计分析。结果表明:不同年份渤海北部东岸海风锋活动的差异较大,海风锋主要出现在6-8月,其中7月最多;海风锋可分为沿山型、北部沿海型和混合型3种,其中沿山型占比70%以上,海风锋东移到达沿山地区后维持加强,北部可伸展到沈阳地区;海风锋在雷达反射率图上表现为窄带回波,强度一般小于27 d Bz,在速度图上表现为风向的辐合或风速的大值区,但在相关系数、差分反射率等雷达双偏振产品上没有可明显识别的特征;在各种天气背景下均能发生海风锋,其中在高空脊控制下最多,且可触发午后热对流,多为弱对流;在副热带高压后部、高空槽、冷涡背景下的海风锋容易触发强对流天气,带来冰雹、短时强降水、雷雨大风等灾害。

We analyzed the characteristics of sea breeze front activities and triggered convection on the eastern coast of the northern Bohai Sea in 2015,2018,and 2019,using convectional observations,data retrieved from radar and satellite and observed at encrypted automatic weather stations. The results showed that the activity of sea breeze fronts in the eastern coast of the northern Bohai Sea varies greatly among years and mainly occurs from June to August,mostly in July. Sea breeze fronts can be divided into three types,including the along-mountain type,the northern-coast type,and the hybrid type. The along-mountain type of sea breeze fronts accounts for more than 70%,which can be maintained and strengthened after moving eastwards to the mountainous area,and extends to Shenyang in the northern part. Sea breeze fronts usually show a narrow-band echo in radar reflectivity,with intensity lower than 27 d Bz,and shows the convergence of wind direction or high wind speed in velocity maps,but no distinct features on radar dual polarization products such as correlation coefficient and differential reflectivity. Sea breeze fronts can occur in the various synoptic background,mostly in the presence of upper-level ridges. They can trigger afternoon heat convection,dominantly as weak convection. Sea breeze fronts in the rear of subtropical highs,in the presence of upper-level trough and cold vortex,tend to trigger strong convection and disasters including hail,short-time heavy rainfall,thunderstorm,and gale.