摘要
利用NCEP1°×1°逐6h分析资料和常规观测资料,从环流形势、垂直热力结构、动力抬升、水汽条件等方面着手,对2008年1月25—28日和2月1—2日江西省罕见大范围冻雨和暴雪过程进行了对比分析。结果表明,2次过程发生在相似的环流背景下,但暴雪过程的饱和湿度层更加深厚,冷空气条件、动力辐合、垂直风切变均强于冻雨过程。对流层中层的爆发性增温是冻雨、暴雪降水相态改变的关键,2次过程在925—700hPa都存在逆温层,但冻雨过程的锋面逆温更强,并在800hPa以上存在1～2km的0℃以上暖层,暖层最高温度为2～7℃;而暴雪过程整层温度均在0℃以下,不存在暖层。强降雪伴随着湿位涡的发展而加强,MPV1正中心附近的强梯度带和MPV2负斜压中心附近的密集等值线,以及深厚、强烈的上升运动对冻雨和暴雪的预报具有较好的指示意义。2次过程在低空都为辐散气流,中层辐合、高空辐散,且辐合、辐散层从高到低,从北向南倾斜分布。暴雪过程的高层辐散更强,高低空的抽吸作用更加剧烈。
Based on NCEP1°×1°6 h interval reanalyzed data and daily observation, the Jan. 25--28 regional freezing rain and Feb. 1-2 heavy snow in 2008 in Jiangxi province were contrasted at the aspects of circulation situation, thermodynamic structure, dynamic lifting and vapor condition. The results show that the two processes had the similar circulation background, but the heavy snow had deeper vapor-saturated layer and stronger cold air, stronger convergence and vertical wind shear than the freezing rain. The temperature increasing quickly in the middle troposphere was the key for freezing rain changing into heavy snow, both of the two processes had temperature inversions between 925--700 hPa. However, for the freezing rain the frontal inversion was stronger, with a 1--2 km warm layer above 800 hPa, in which the highest temperature was 2--7 ~C, while for the heavy snow the temperature was below 0℃ in the whole troposphere. The heavy snow developed with the moist potential vorticity. High gradient region near the MPV1 positive center, dense isoclines area near the baroclinic center, and deep strong ascending motion can indicate freezing rain and heavy snow. Both of the two processes had lower-layer divergence, mid-level convergence and upper-layer divergence, with the convergence and divergence inclining northward to the southward from upper to lower layer. The heavy snow had more significant upper-layer divergence and pumping action.
出处
《气象与减灾研究》
2008年第2期29-35,共7页
Meteorology and Disaster Reduction Research
基金
江西省气象局2008年重点科研项目"江西冻雨
大雪
冰冻预报方法研究"
关键词
冻雨
暴雪
锋面逆温
暖层
垂直风切变
Freezing rain, Heavy snow, Frontal inversion, Warm layer, Vertical wind shear.
