Abstract: Based on the observational data of acid rain and the surface and high-level meteorological data in Dandong from 2009 to 2013,the spatial and temporal characteristics of acid rain were analyzed,and the pH value in precipitation and frequency of acid rain under different weather conditions were investigated using a correlation analysis method.This study is aimed at providing a scientific basis for the evaluation and prediction of acid rain.The results show that the distribution of pH values of acid rain is uniform in Dandong.Both of the pH value in precipitation and the frequency of acid rain have an increasing trend during the study period,and the smallest pH value in precipitation and the largest frequency of acid rain occur in autumn.The pH value in precipitation is closely related to precipitation magnitude,and fog favors to enhance the precipitation acidity.The southerly winds prevail at ground when acid rain occurs in Dandong.There is an obvious difference in the effects of surface wind speed on the intensity of acid rain during the early stage and the middle stage of precipitation.The pH value in precipitation is mainly determined by the 24-h temperature deviation,the 12-h wind direction before precipitation,and wind speed at 850 hPa during precipitation.The southerly wind is dominant at 850 hPa during acid rain events.Temperature inversion and K index strongly influence the acid rain pollution.

Key words: Acid rain, pH value in precipitation, Acid rain frequency