Abstract: This paper systematically analyzes the temporal variability of the mass concentration of PM_2.5 in Shanghai,and discusses the effects of meteorological factors on the concentration of PM_2.5.It reveals the temporal variability of the PM_2.5 concentration and the status of atmospheric pollution in recent years in Shanghai through multi-scale statistics,qualitative analysis and quantitative computation on meteorological data provided by China Air Quality Online Monitoring and Analysis Platform,as well as China Meteorological Administration.The correlation analysis is applied in understanding the relationship between the PM_2.5 concentration and meteorological factors (the temperature,air pressure,the relative humidity,wind direction,wind speed and precipitation) in Shanghai from 2012 to 2016.The results showed that most of the time the air quality in Shanghai has been good or excellent in recent 5 years and the number of days when it was suffered from the pollution has been decreasing.The PM_2.5 concentration displayed a seasonal feature which indicated a lower value in the summer and a higher value in the winter with the lowest value in August of 16~36 μg·m^-3.The daily variation shows a structure of two peaks and two valleys,with the concentration peaks occurred during 8:00 AM to 9:00 AM and 7:00 PM to 8:00 PM higher during the latter period.The thresholds of the temperature,the air pressure and the relative humidity were 9.8℃,1 021.6 hPa and 83% respectively which were normally the inflection points of the PM_2.5 concentration.There was a logarithmic relationship between the maximum PM_2.5 concentration and the accumulated wind speed and precipitation.When the accumulated wind speed of northeaster and southeaster reached 350 m·s^-1,the PM_2.5 concentration was decreased to 35 μg·m^-3.The bigger the precipitation was,the lower the concentration of PM_2.5 became.This paper showed a good correlation between meteorological factors and the concentration of PM_2.5,and its numerical model had a positive effect on the prediction of the concentration of PM_2.5 and the treatment for atmospheric environment.

Key words: PM_2.5 concentration, pollution characteristics, meteorological factors, correlation