2009年冬季黄河中游一次由旱转雨雪天气的诊断分析  

Diagnosis Analysis on Precipitation in the Middle Reach of Yellow River in the Winter,2009

作　　者：赵桂香[1,2] 秦春英[3] 赵彩萍[4] 张运鹏[5] 董文晓[1] 范英东[6] 

机构地区：[1]山西省气象台,山西太原030006 [2]中国科学院大气物理研究所LASG实验室,北京100029 [3]山西省气象影视中心,山西太原030002 [4]山西省太原市气象局,山西太原030002 [5]中国气象局国家卫星气象中心,北京100081 [6]黄委会中游水文水资源局,山西榆次030600

出　　处：《高原气象》2010年第4期864-874,共11页Plateau Meteorology

基　　金：中国科学院大气物理研究所LASG开放课题"基于条件非线性最优扰动的暴雨集合预报试验";山西省气象局重点科研项目(0509;0702)共同资助

摘　　要：针对2009年2月7～8日持续干旱近百天的黄河中游地区出现的转折性雨雪天气,利用实况资料计算了等熵温度梯度、可降水量、水汽通量及其散度、相对湿度、垂直速度等,分析了熵分布及演变、干侵入、水汽场特征等,结果表明:(1)这次降水出现在500hPa环流形势平直,极地冷空气活动较弱,在地面回流高压呈东西向带状分布的背景下,系统浅薄,降水量级难以把握。(2)熵诊断揭示,500hPa等熵梯度大值区的出现对未来12～24h强降水有先兆指示意义,强降水中心出现在500hPa等熵梯度大值区与700hPa温度露点差<3℃的叠加区。(3)水汽诊断表明,强降水出现前,黄河中游及其上游西南地区的可降水量显著增加,为强降水的出现提供了水汽的积聚,而降水开始后,低空超低空东南急流则是水汽的主要补充来源;强降水并不是出现在水汽通量大值区内,而是在水汽通量大值区西北侧、等值线密集带附近,同时又有风辐合的区域。(4)这次雨雪过程中,干冷空气主要来自对流层高层,在雨雪区上空的垂直分布呈"漏斗"状,该过程中从贝加尔湖地区南下的西北和东北气流沿漏斗壁下滑向低层传播;而中低层湿区呈倒扣的"碗状"向上伸展,中低层西南和东南两支暖湿气流沿"碗壁"爬升,在对流层中层耦合加强,与干冷空气交汇,产生强降水。(5)对流层高层持续的干侵入,使得中低层切变线稳定维持,有利于其前方西南急流的稳定加强和对流性不稳定的持续发展,是导致强降雪持续、增幅的重要原因。(6)强降水出现在地面中尺度辐合稳定加强期间,降水落区在辐合区及其东南侧;辐合区内强烈的上升运动是触发不稳定能量释放,使熵由不平衡达到平衡的重要机制。Based on the observed data,the rain or snow weather occurred in the middle reach of Yellow River from 7 to 8 February 2009,are analyzed.The results show that： （1） Under the background of straight west flow circulation at 500 hPa,the weak cold air in the-polar region,and the Mongolian high on the surface having east-west flow band distribution this process of rain or snow weather occurred.The system is shallow and it is difficult to predict precipitation weather.（2） The entropy diagnosis shows that the occurrence of great value area of isentropic gradient at 500 hPa has an indication on heavy precipitation-next 12 to 24 hours,and the centre of heavy precipitation-located at superposition between the isentropic temperature gradient at 500 hPa and dew point temperature difference less than 2℃-at 700 hPa.（3） The diagnosis-analysis of water vapor shows that the precipitable water in the middle reach of Yellow River and its upstream southwest before heavy precipitation significantly-increased,and it provided accumulation of water vapor for heavy precipitation,while after the precipitation,southeast LLJ became main complement.（4） In this process,the dry cold air mainly came from troposphere-high-level and its distribution was a ＂funnel＂-shape,the northwest airflow and northeast airflow from Lake Brakal glissaded along ＂funnel＂-wall and spreaded down.While the wet area at low was a flip ＂bowl＂-shape and it spreaded upwards.The heavy precipitation-caused by intersection-between the dry-cold air and southwest and southeast warm airflow climbed along ＂bowl＂-wall.（5） The sustained dry intrusion from tropospheric high-level made the shear line at low maintain stable,in favor of making SWJ strengthen steadily and convective instability develop-sustainably.It is one of important reasons lead to heavy snow increase continually.（6） The heavy precipitation occurred-during the mesoscale convergence on the surface stable increasing,the rainfall drop-zone located at convergent area and its

关 键 词：黄河中游 熵 干侵入 中尺度辐合 

分 类 号：P458.121[天文地球—大气科学及气象学]