Multi-yearly changes of atmospheric mixed layer thickness and its effect on air quality above Chongqing

Based on the daily meteorological observation data from 2000 to 2005,frequency distribution and time variation of atmospheric mixed layer thickness were analyzed by the methods established in the national standard GB/T 3840—91.Furthermore,the correlation between mixed layer thickness and air pollution index(API) was also discussed as a case study of 2005.The results show that the mixed layer thickness from 0 to 800 m is the most frequent,and the average value is 428 m.The seasonal and daily variations are obvious.Compared to that in 1980—1990,the annual average mixed layer thickness in 2000—2005 increases in general.Correlation analysis indicates that the mixed layer thickness is negatively correlated with API(r=-0.72),which suggests that the mixed layer thickness is an important factor influencing air quality in Chongqing.