2010-2019年春季影响大连的温带气旋特征及爆发性气旋成因分析

利用常规和加密气象观测、NCEP再分析、云图等资料，对2010—2019年春季影响大连的温带气旋特征及爆发性气旋造成的极端天气的物理机制进行分析。结果表明：春季进入到渤海、黄海北部的气旋平均每月2.4个；气旋一般先进入黄海，进入黄海和经渤海进入黄海的温带气旋总计有84.5%进入黄海北部，且春季进入黄渤海的气旋73%会给大连地区带来大风或降水天气，影响大连东部沿海的几率远高于其他地区；产生较强灾害性天气的爆发性气旋多发生在春季，路径基本都是由西南向东北方向移动。爆发性气旋主要是因为温带气旋经过黄渤海后短时间快速降压，到大连陆地发生爆发性发展，这种温带气旋的发展一般从低层开始，具有较强的锋区和斜压性，爆发阶段位于正涡度平流最大的高空急流出口区，对应低空位于低空急流左前方辐合区。较强的冷、暖温度平流是造成极端降水和大风天气的主要因素，暴雨的形成主要是温带气旋带来的暖湿气流持续输送，并伴有较强上升运动促使的水汽垂直输送，整层水汽充沛；当低空急流发展和冷、暖空气交绥时，出现了在高湿、高温的湿斜压锋区上的强降水；而北路强冷空气与黄、渤海上爆发性发展的温带气旋形成极强气压梯度，是出现极端大风的主要原因。

Characteristics of extratropical cyclones affecting Dalian and causes of outbreak cyclones in spring during 2010 to 2019

We analyzed the characteristics of spring extratropical cyclones affecting Dalian and the physical mechanism of extreme weather caused by outbreak cyclones using conventional and intensive meteorological observation data from 2010 to 2019, the National Centers for Environmental Prediction (NCEP) reanalysis data, satellite cloud images, etc.The results show that the number of extratropical cyclones entering the Bohai and the northern Yellow Sea is 2.4 per month.Cyclones usually enter the Yellow Sea at first, and 84.5% of the extratropical cyclones (including entering the Yellow Sea directly or through the Bohai Sea) can enter the northern Yellow Sea.In spring, 73% of the cyclones entering the Bohai and the Yellow Sea can cause strong winds or precipitation in Dalian, and their effect probability on the eastern coast of Dalian is much higher than on the other areas.The outbreak cyclones causing severe disastrous weather occur most frequently in spring, with the paths moving from the southwest to the northeast.The occurrence of outbreak cyclones is mainly due to the quick decline of extratropical cyclones pressure in a short period after cyclones passing the Bohai and the Yellow Sea and their explosive development in the land of Dalian.The extratropical cyclones usually develop from the lower levels with significant frontogenesis and baroclinity.The outbreak development of the cyclones occurs in exit areas of the upper-level jets with the strongest positive vorticity advection and corresponds to the left front convergence of the low-level jets at lower altitudes.Strong cold and warm temperature advection are major reasons for extreme precipitation and strong winds.The formation of a rainstorm is mainly due to the continuous transport of warm and wet air brought by extratropical cyclones.Vertical transport of water vapor driven by strong ascending motion moistens a whole layer.When low-level jets develop and cold and warm air masses intersect, strong precipitation occurs at the moist baroclinic front with high humidity and temperature.Strong cold air from the north and the extratropical cyclones on the Bohai and the Yellow Sea contribute extremely strong air pressure gradient, which is the main reason for extremely strong winds.