Abstract: The characteristics and variations of the intensity and occurrence frequency of acid rain at the annual,seasonal,and monthly scales as well as its meteorological impact factors were analyzed in this study,using the observational data of acid rain in Zhenjiang from January of 2008 to December of 2012.The results show that all the annual,seasonal,and monthly mean pH values of acid rain are relatively small,the intensity of acid rain is strong,and the occurrence frequency of acid rain is usually high in spring and autumn.Considering the effects of meteorological parameters such as precipitation,wind direction,temperature inversion,and the vertical transport of non-local pollutants,it is found out that both of the occurrence frequency of acid rain and its proportion to the total precipitation are large.More than half of the acid rain in Zhenjiang occurs under the northeasterly,southeasterly,and easterly wind conditions.Acid rain in Zhenjiang is also related to the pollutants transport from other regions,probably including the northern China region,the eastern China region,Hu'nan province,and Hubei province.The deep temperature inversion in the lower troposphere (at and below 925 hPa) usually favors the occurrence of acid rain,and the acid rain intensity is associated with the temperature inversion intensity,which means the temperature deviation in the inversion layer is larger,the pH values is smaller,and the acid rain intensity is larger.

Key words: Acid rain, Intensity, External pollution sources, Temperature inversion