一次雪面降温引起的异常寒冷天气分析

THE DIAGNOSIS ANALYSIS FOR THE UNUSUALL COLD WEATHER DUE TO THE DETEMPERATURE OVER SNOW COVER

中文关键词:  雪面降温  冷高压  下坡气流  超低空急流

英文关键词:Air detemperature above snow surface  Cold high pressure  Orographic downward wind  Extra low leveljet

中文摘要:

      本文通过两次同日期而不同年份的异常寒冷天气的对比分析,揭示了内蒙东部雪面空气降温形成的强冷高压。计算了雪面辐射引起的近地面气层降温,其结果与实况很接近。参照气团垂直减温率算得雪面空气的净降温值。强冷高压在北高南低地形上气流顺坡南下,在津京冀近地面气层形成了超低空急流,促使当地气温剧烈下降,且其降温强度与内蒙的雪面降温值非常吻合。最后,按地形上空温压分布的力管场结构给出了发生下坡风的物理图像。

英文摘要:

      In this paper, the formation process of cold high pressuredue to the radiation cooling over the snow surface at the east of Nei Menggu was revealed by contrast analysis for two heavy cold weater cases. The near surface layer air detemperature due to snow cover radiation colling was calculated according to the Brunts effective radiation formulation, and the detemperature was estimatedy etaccording to the normal lapserate of temperature. The values from two methods all were very near the observational fact. In the south of cold high pressure the cold air from the plateau down along the slop south-ward, and the extra low level jetoccurred over Beijing Tianjin and Heibei. So the surface temperature dropped sharply in this region, and the detemperature value was near the value in the east of Nei Menggu. The physical mechanism for the occurence of orographic downward wind was shown in the solenoid field.