湖北省冬季大雪成因分析与预报方法研究

Study on Formation Mechanisms and Forecast Method of Winter Snowstorm in Hubei Province

针对湖北省冬季大雪天气预报难题,使用常规观测资料和数值预报产品,分析了1988—2005年发生在湖北省冬季的15次大雪过程。结果表明,地面冷空气、700 hPa江南西南急流和500 hPa西风带低槽是决定湖北省冬季大雪的三个主要天气系统,700 hPa江南西南急流强弱决定湖北省大雪强度,地面冷空气强度决定湖北省降温幅度;归纳出有利湖北省大雪的温度条件的垂直分布特征;由于锋面抬升和西南低空急流的作用,在对称不稳定条件下产生倾斜上升和下沉运动,形成中尺度倾斜环流,在充沛环境水汽条件下,产生大雪天气;采取物理参数指标结合数值预报建立的湖北省大雪客观预报方法,在实时预报业务中预运行效果较好。

The snowstorm forecast in winter is one of the difficult problems of weather forecast in Hubei province. By using the conventional observational data and numerical forecast products, the snowstorm in Hubei province during 1988--2005 were analyzed. The results suggested that the chief weather systems which contribute to the snowstorm were the ground cold air, southwest jet of 700 hPa in the south of the Yangtze River and westerly through of 500 hPa. The southwest jet of 700 hPa in the south of the Yangtze River is related to the intensity of snowstorm. The ground cold air affect on the degree of temperature decrease. It is summed up the vertical distribution of temperature characteristics favourable for snowing in Hubei Province. Because of the frontal uplift or the southwest low level jet stream, the tilted mesoscale circulation was formed in the symmetric instability with the tilt rising and sinking movement. Under the both conditions of mesoscale circulation and abundant water vapor the snowstorm generated. The method of objective forecasting snow in Hubei Province established with the physical parameters and numerical prediction has a better performs in real-time forecasting.