兰州市霾日的气候特征

利用1961-2006年的常规气象资料分析了兰州市霾日的气候特征.研究表明20世纪70,80年代兰州市霾日发生较频繁,但整体呈减少趋势,尤其90年代开始大幅下降;兰州的霾日一年内各季均有发生,但主要发生在秋末和冬季,12月份最多,强度最强的霾日也集中在冬季;时次分布上春、夏季8:00出现霾日最多,而秋、冬季14:00最多;一年中霾日数成U型分布,与地表气温呈负相关,气温越低,霾日出现的概率越高;风速小于2m/s和日平均相对湿度低于70%也是霾发生的主要气象条件之一.

Analysis of climate characteristics of haze in Lanzhou City

Climate characteristics of haze were analyzed by using conventional meteorological data from 1961 to 2006 in Lanzhou City. Due to severe pollution, haze in Lanzhou frequently occurred during 1970's to 1980's. However, the hazy days in total were decreasing in 1990's and at the turn of the century. Haze occurred in the four seasons of any year throughout the history but mostly in late autumn and the whole winter. Of twelve months, the maximum days of haze occurrence are in December and the most strong are also in winter. As for a daily distribution, the great part of haze appear at 8:00 in spring and summer,14:00 in autumn and winter. In a year, the variations of haze days display a U type, which has negative correlation with temperature. According to statistic results, the lower the surface temperature is, the more likely that haze occurs. The wind speed below 2 m/s and relative humidity under 70% are two major weather conditions causing haze occurrence.