2011年与2008年贵州低温雨雪冰冻天气锋区特征对比

Comparative Analysis on the Frontal Zone Feature of Two Freezing Rain and Snow Weather Processes in 2008 and 2011 in Guizhou Province

用常规气象观测资料和NCEP 2.5°×2.5°再分析资料,对贵州2011年年初和2008年年初2次严重低温雨雪冰冻灾害期间的天气形势、冷空气、水汽和大气层结等特征进行了分析比较。结果表明:静止锋是贵州低温雨雪冰冻天气的主要天气系统;2008年较2011年冷暖空气均较强,故锋区强、锋面坡度较小,这是2008年冰冻天气强于2011年的主要原因;冻雨的发生与层结的逆温有很大关系,逆温发展的阶段均能较好地对应每一次冰冻过程;逆温强度强且长时间存在是2008年冰冻天气持续时间长的原因。2次过程中低层锋区附近有明显的水汽辐合,形成雨雪天气;对2011年降雪和冻雨过程的对比分析表明降雪与冻雨最明显的特征是降雪时层结基本无逆温,逆温层的出现是降雪转换成冻雨的重要原因。

Based on the conventional observation data and NCEP 2.5 ° x 2.5° reanalyzed data, the comparative analysis of the synoptic situation, cold air, water vapor and the atmospheric stratification was done between two heavy cryogenic freezing rain and snow weather processes which occurred in the beginning of 2008 and 2011, respectively. The results show that the stationary front was the main weather system of the freezing rain and snow weather in Guizhou. The principal reason why the freezing rain and snow weather in 2008 was stronger than the one in 2011, was that both the cold and warm airs were more active and therefore the frontal zone was stronger and frontal slope was smaller. The occurrence of freezing rain had great relation to the inversion layer, the development of the tempera- ture inversion brought the corresponding change in each freezing rain weather process. The process in 2008 had a long duration because of the excellent strength and prolonged existence of the inversion layer. It was the obvious moisture convergence near frontal zone at the middle and low level which caused the freezing rain and snow weather in these two processes. During the the freezing rain and snow weather process in 2008, there was almost no temperature inversion during snowfall stage and the appearance of the inversion layer was the momentous factor which transformed snow into freezing rain.