2017年沙颍河流域一次暴雪天气成因分析  

Causes Analysis of the Snowstorm Occurring in the Shaying River Basin in 2017

作　　者：顾佳佳 单铁良 Gu Jiajia;Shan Tieliang(Luohe Meteorological Office of Henan Province,Luohe 462300,China;Shaying River Basin Meteorological Center of Henan Province,Luohe 462300,China)

机构地区：[1]漯河市气象局,河南漯河462300 [2]河南省沙颍河流域气象中心,河南漯河462300

出　　处：《气象与环境科学》2022年第5期23-31,共9页Meteorological and Environmental Sciences

基　　金：河南省气象局预报员专项(KY201932);漯河市气象局沙颍河流域气象科技创新团队。

摘　　要：利用常规和非常规观测资料、NCEP 0.25°×0.25°高分辨率分析资料,对2017年2月21日沙颍河流域暴雪过程的成因进行分析。结果表明:(1)500 hPa上河套低槽与低纬南支槽东移合并,槽前强盛的西南急流与东路扩散南下的底层强冷空气结合,是河南典型的暴雪形势。先有中低层暖湿气流输送,而后底层强冷空气南下导致冷垫不断增厚,降雪强度大、持续时间短,这不同于以往河南持续暴雪过程。(2)持续的水汽输送与较强水汽辐合为暴雪天气提供了充沛的水汽条件;较强正涡度区及高空辐散抽吸作用与低层辐合叠加,形成深厚上升运动,是暴雪发展的有利动力条件。(3)次级环流上升支与锋生中心、强降雪区三者对应较好。低层出现垂直锋面的正次级环流,冷空气下沉,暖湿气流上升,锋生作用增强;同时次级环流的两个上升支叠加导致上升运动进一步增强。负MPV明显增强时,CSI增强,降雪增大。(4)雷达回波演变特征反映了雨雪加强、维持、减弱等变化。强降雪回波强度多为30~45 dBZ,回波高度在6 km以下,反映了稳定性降雪特征;0℃亮带变化反映雨雪转换特征。Based on the conventional and unconventional observation data and NCEP 0.25°×0.25° reanalysis data, the causes for the snowstorm that occurred in the Shaying River basin on the February 21, 2017 is analyzed. The results show that:(1)Under the background that the 500 hPa low trough merged eastward with the south branch trough in low latitudes, the strong southwest jet in front of the trough, which was combined with the strong cold air from the bottom of the east road spreading southwards, was the typical situation for the snowstorm in Henan Province. The warm humid air flow in the middle and low layers was transported first, and then the strong cold air from the bottom layer led to the thickening of the cold pad. So the heavy snowfall intensity and short duration was different from those of continuous snowstorms of Henan in the past.(2)Continuous water vapor transport and strong water vapor convergence provided plentiful water vapor conditions for the snowstorm. The strong positive vorticity area and the effect of high-level divergent suction superimposed with low-level convergence formed a deep ascent movement, which was the favorable dynamic condition for the development of snowstorm.(3)The ascending branch in the secondary circulation corresponded well with the frontal center and the strong snowfall area. The positive secondary circulation vertical front appeared in the lower layer. The sinking cold air and the rising warm-humid air made frontogenesis increased. Besides, the superposition of the two ascending branches of the secondary circulation caused the ascent movement to be further enhanced. When the negative MPV was significantly enhanced, the CSI was enhanced and the snowfall increased.(4)The evolution characteristics of radar echoes indicate that snowfall strengthened, maintained and weakened. Strong snowfall echo intensity was between 30—45 dBZ, and the echo height was below 6 km, reflecting the stable snowfall characteristics. The change of the bright band at 0 ℃ layer reflected the characteris

关 键 词：沙颍河流域 暴雪 锋生与次级环流 条件性对称不稳定 雷达回波 

分 类 号：P426.63[天文地球—大气科学及气象学]