西藏南部特大暴雪的动力成因分析  

Analysis of the dynamic causes of the extremely heavy snowfall in southern Xizang

作　　者：奚凤 旦增冉珍 边玛罗布 丹增诺布 余燕群 Xi Feng;Danzeng Ranzhen;Bianma Luobu;Danzeng Nuobu;Yu Yanqun(Meteorological Observatory of Xizang Autonomous Region,Lhasa 850000,China)

机构地区：[1]西藏自治区气象台,拉萨850000

出　　处：《西藏科技》2024年第12期33-40,共8页Xizang Science And Technology

基　　金：西藏自治区自然科学基金项目(XZ202401ZR0098);西藏地方标准项目;中国气象局天气预报复盘研究项目(FPZJ2023-126)。

摘　　要：利用西藏地面观测降水资料和欧洲中期天气预报中心(ECMWF)ERA5再分析资料,采用动力学诊断方法分析了2020年1月16—18日西藏南部的特大暴雪过程。研究结果表明:在藏南地区喇叭口地形作用下,偏南和西南暖湿气流沿山坡爬升,造成低层暖湿上升气流与干燥冷空气形成不稳定大气层结,有利于暴雪天气过程的发生;低空强辐合抬升和中高空辐散抽吸作用是引发特大暴雪的主要动力机制;垂直螺旋度“下负上正”的结构为暴雪过程预报提供有益的指示,当螺旋度整层为一致正值时也会产生较强的降雪,而暴雪的强度大小随着较低层正螺旋度中心值的迅速升高而加强,中心值越大说明降雪的强度越强;MPV1为“上正下负”的垂直结构,同时MPV2<0,MPV1和MPV2的绝对值增长迅速时和降雪增幅一致。Based on the MICAPS surface observation precipitation data of Xizang and the European Center for Medium-Range Weather Forecasts(ECMWF)ERA5 reanalysis data,the dynamic diagnostic method was used to analyze the extremely heavy snowfall in southern Xizang from January 16 to 18,2020.The results show that under the influence of the trumpet topography in southern Xizang,the southerly and southwesterly warm and humid airflow climbs along the mountain slope,resulting in the formation of unstable atmospheric stratification between the low-level warm and humid updraft and the dry and cold air,which is conducive to the occurrence of blizzard weather.The strong convergence uplift at low altitude and the divergent suction at mid-high altitudes are the main dynamic mechanisms that cause heavey snowfall.The structure of vertical helicity"negative at bottom and positive on top"provides a useful indication for the prediction ofblizzard process,and strong snowfall will occur when the whole layer of helicity is a consistent positive value,and the intensity of blizzard increases with the rapid increase of the center value of the positive helicity in the lower layer,and the larger the center value,the stronger the intensity of snowfall.MPV1 is a vertical structure with"positive on top and negative at bottom",and when MPV2<0,the absolute value of MPV1 and MPV2 increases rapidly,which is consistent with the increase in snowfall.

关 键 词：高原特大暴雪 动力特征 垂直结构 垂直螺旋度 湿位涡 

分 类 号：P45[天文地球—大气科学及气象学]