江西一次大雾天气诊断分析和ECMWF集合预报产品释用

利用常规气象资料,对2013年11月15日出现在江西省北部地区的一次大雾天气过程进行了诊断分析,并利用ECMWF集合预报产品对该大雾天气过程的预报进行了解释应用。诊断结果表明,该次大雾天气过程是一次典型的辐射雾。14日傍晚到夜间,江西省北部地区转处冷高压控制,阴转晴,冷空气和地面辐射共同造成的冷却作用明显;大雾发生时的逆温层高度大约在981 hPa;1—3 m/s的风速有利于形成较厚的冷却层;地面相对湿度大,水汽充足。通过对ECMWF集合预报的气温、地面湿度、地面风速和天空总云量预报产品的释用,可以在大雾出现的前日判断出江西省西北部地区同时满足辐射雾出现4个条件(水汽、晴空辐射冷却、微风、近地层的稳定层结)的概率最大,因此出现大雾的可能性最大;江西其他地区不能同时满足4个条件,出现大雾天气的可能性很小。随着对集合预报产品的不断深入挖掘,可以进一步提高集合预报对大雾等灾害性天气的预报能力。

Diagnostic Analysis and ECMWF Weather Ensemble Forecast Products Application for a Heavy Fog Process in Jiangxi Province

By using the conventional meteorological data and the ECMWF ensemble prediction products, a fog weather event occurred in northern Jiangxi on 15 November 2013 was analyzed. The diagnostic results show that the fog event was a typical radiation fog. From evening to midnight on 14th, the northern region of Jiangxi province was controlled by cold high-pressure with clear sky. An obvious cooling effect occurred due to cold air and ground radiation. There was an inversion layer at about 981 hPa level with 1-3 m/s wind speed, high surface relative humidity and abundant water vapor which was conducive to the formation of the thick cooling layer. According to analyses of temperature, surface humidity, surface wind speed and the total cloud amount products of ECMWF ensemble forecast, it could be judged that before the fog occurred, the possibility to meet the four necessary conditions for radiation fog formation in northwestern Jiangxi was maximum. With the continuous interpretation of ensemble prediction products, the ensemble prediction for fog and other weather disasters prediction ability can be further improved.