2023年6月1日辽宁龙卷过程多尺度特征及成因分析
Analysis of multi-scale characteristics and causes of the tornado process in Liaoning province on June 1, 2023
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摘要: 利用加密自动站、FY-3G低轨气象卫星、多普勒雷达及历史观测数据等资料, 对2023年6月1日发生在辽宁北部的系列龙卷天气过程进行诊断分析。结果表明: 东北冷涡为此次对流天气提供干冷条件, 地面气旋前部偏南气流向北输送暖湿空气, 辽宁北部形成强的对流不稳定。低层存在近乎垂直分布的锋区, 锋前950~750 hPa高度正涡度与垂直速度有较好的配合, 动力抬升作用增强, 利于对流系统的发展。伴随中尺度锋区出现的干线、温度梯度大值带以及冷池导致辽西生成线状对流云带, 局地小尺度涡旋是产生阜新龙卷的动力触发系统。辽宁北部较强冷池与东南部的强暖脊之间产生的密度流造成冷池东侧局地偏西风增大, 风速、风向辐合以及较强冷池3个有利条件在开原附近叠加, 是触发开原龙卷的原因。在东北冷涡背景和辽宁西部沿海沿山的特殊地形作用下, 辽宁北部容易出现产生龙卷的对流潜势条件, 阜新三面高、中间低的倒“U”型特殊地形利于小尺度的气旋性闭合环流的形成, 可能是阜新为辽宁龙卷中心的原因之一。Abstract: A series of tornado weather processes that occurred in northern Liaoning province on June 1, 2023 were diagnosed using the data from intensive automatic stations, FY-3G low-orbit meteorological satellites, Doppler radar and historical data. The results show that the northeastern cold vortex provides dry and cold conditions in the upper levels, and the southerly air flow in the front of the surface cyclone transports warm and humid air to the north, forming a strong convective instability in northern Liaoning province. In the lower levels, there is a nearly vertically distributed frontal zone. The high positive vorticity at the 950~750 hPa in front of the frontal zone is well matched with the vertical velocity, and the dynamic uplift effect is enhanced, which is conducive to the development of the convective system. The dry lines, large temperature gradient zones and cold pools associated with the mesoscale frontal areas lead to the formation of linear convective cloud belts in western Liaoning province. Local small-scale vortices may be the dynamic trigger system for the tornado in Fuxin. The density flow generated between the strong cold pool in northern Liaoning province and the strong warm ridge in the southeast caused the local westerly wind to increase on the east side of the cold pool. The superposition effect of the wind speed and direction convergence along with the strong cold pool may be the reason for the triggering of the tornado in Kaiyuan. Under the background of the northeastern cold vortex and the special coastal and mountainous terrain, northern Liaoning province has the convective potential conditions for tornadoes. Fuxin is located in the special terrain of an inverted "U" shape with high altitude in the surrounding area and low in the middle. It is easier to form small-scale cyclonic closed circulation, which may be one of the reasons why Fuxin is the center of the Liaoning province tornado.
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