我国中东部一次大范围霾天气的分析

Analysis of a Large-scale Haze over Middle and Eastern China

利用空气污染资料、常规气象观测资料和NCEP再分析资料,对2007年2月5日我国中东部大范围霾天气进行了综合分析。结果表明:前倾槽结构和逆温层结为霾的形成提供了有利条件;800hPa以下层垂直速度、涡度和散度的绝对值较小,是霾维持的动力因子。大气混合层高度的变化对霾的生消有很好指示作用,霾天混合层高度北高南低分布,致使南方比北方更易出现严重霾天气。此外,要素对比结果表明,霾的相对湿度比雾低,温度露点差比雾大,逆温强度比雾弱,大气混合层高度比雾高,这些可为霾的预报提供参考依据。

A large-scale haze process that happened on Feb. 5,2007 over middle and eastern China was analyzed based on the air pollution index, conventional observation data, and NCEP reana- lyzed data. The results show that both the forward-tilling trough and the temperature inversion are favorable condition for the haze formation. The absolute values of vorticity, divergence and vertical velocity below 800hPa are all quite smaller, which favorites to the persistence of haze. The variation of air mixing height is a good indication to the formation and disappearance of the haze. The mixing layer height appears higher in North China than that in South China during the haze periods, which makes it easier to form heavy hazy weather in South China. In addition, it was found that the relative humidity is lower, the difference between air temperature and dew temperature is higher, the intensity of air temperature inversion is weaker and the mixing layer height is higher in the haze periods than in the fog periods, which can provide some helpful clew for haze forecasting.