渤海湾地区碰撞型海风锋天气过程的资料诊断分析

Data Analysis of Collision-Type Sea-Breeze Front in the Bohai Bay Region

利用多普勒雷达资料和地面自动站以及再分析资料对近年来7次典型的渤海湾地区碰撞型海风锋天气过程进行了分析。资料分析显示对流系统正面碰撞海风锋时(偏东西向碰撞)得到显著发展,而追赶碰撞海风锋时(偏南北向)则没有明显加强。海风锋移动沿途近地面出现明显的降温和风切变可以帮助判断海风锋的移动位置。高层稳定的偏西风有利于引导对流系统与西进海风锋发生正面碰撞。而低层的风场辐合则有利于碰撞过程中对流运动的发生,同时副高西北侧的水汽输送为降水的形成提供了有利条件。渤海湾地区地形的热力效应形成的低层偏中性层结有利于对流运动的发生,另外,在高空偏西风环境下地形可能对与海风锋碰撞的对流系统的触发或加强有促进作用。

Seven typical cases of collision-type sea-breeze front happened in the Bohai Bay region of China, are analyzed with observational （Doppler radar and surface stations） and reanalysis data. The analysis shows that convective systems significantly develop when they hit the sea-breeze front from its front, rather than its rear. A steady upper level westerly favors steering convective systems to move eastwardly and collide with the sea-breeze front. Lower level wind convergence enhances the occurrence of convective motion during the collision, and the water vapor transportation by the flow at the northwest edge of the subtropical high favors the formation of precipitation. The neutral atmospheric stratification at the lower level, caused by a topographic thermal effect, also promotes the occurrence of convective motion. The dynamical effect of topography may enhance the triggering or intensifying nature of the convective systems colliding with the sea-breeze front under the condition of the upper level westerly.