浙东冬季和夏季两次强雷暴天气过程对比分析

利用多种观测资料,结合NCEP再分析资料,对比分析了浙东冬季和夏季两次强雷暴过程中的各种环境条件,结果表明:以对流有效位能CAPE表达的深厚湿对流潜势条件夏季个例的比冬季的好,二者分别为1148 J·kg~(-1)和490 J·kg~(-1)。冬季个例的动力抬升条件更好:低层到地面受冷锋影响;700、850 h Pa因急流风向风速的不连续而产生较强的辐合;500 h Pa处于长波槽前的上升气流中,最大的垂直速度达1.1 Pa·s~(-1)。两次过程的共同特点是强回波分布与地面θ_(se)高值区和切变线叠加区对应关系比较好,为雷暴系统的临近预报提供了重要线索。地面有冷锋影响时,要考虑冷锋入海后风力加大,地面辐合加强,使对流发展。由海陆不同比热属性造成的海陆之间白天和夜间的不同温差,对白天和夜晚系统入海后的强度变化有不一样的影响。10个浙东冬季雷暴个例天气形势分析结果表明,冬季雷暴的共同特点是都有冷暖空气在浙东强烈交汇,华南到华东中低层有很强的西南急流,850 h Pa最大风速达到20 m·s~(-1)以上。两季雷暴各种对流参数对比分析结果显示,冬季雷暴比较好的预报指标是总指数和垂直风切变,重点关注西南急流的强度、冷锋和850-500 h Pa的对流稳定性及动力抬升条件。

Comparison Analysis of Two Severe Thunderstorms Occurred in Summer and Winter in Eastern Zhejiang Province

Based on various observation data and the meteorological reanalysis data of NECP, in this paper, sorts of environmental conditions of a severe winter thunderstorm and a severe summer thunderstorm in eastern Zhejiang province were analyzed. The results showed that the value of convective effective potential energy in the summer case (1148 J·kg-1) was higher than that in the winter case (490 J·kg-1). The dynamic conditions of the winter thunderstorm were better. The low to the ground was affected by cold front. The 700, 850 hPa due to the turbulent wind speed of the discontinuous generated strong convergence. The 500 hPa was in the upward flow in front of the long wave slot, and the largest vertical speed reached to 1.1 Pa·s-1.The two weather processes had a common feature in effective corresponding relation between distribution of strong echoes and superposition area where had high potential pseudo equivalent temperature on the ground and shear lines. The characteristic played an important role in nowcasting of thunderstorms.When a surface cold front moved to the sea, the convergence of wind and intensity of convective systems would enhance on account of strong wind speed. Because of different specific heat between sea and land, temperature differences during day and night were produced. As a result, intensity change of the systems moved into the sea would equally different. The weather situation of 10 eastern Zhejiang thunderstorm cases were analyzed, and the common characteristic was that there was a strong intersection of warm and cold air in eastern Zhejiang.The strong southwest rapids in the middle and lowerin South China reached East China, and the 850 hPa maximum wind speed reached more than 20 m·s-1. Comparative analysis of the convective parameters of two season thunderstorm showed the better prediction index for winter thunderstorm were the total index and the vertical wind shear, focusing on the intensity of the southwest jet, the cold front and convection stability and dynamic uplift conditions of 850-500 hPa.