Abstract:

Variations of PM_2.5 mass concentrations and meteorological factors and the impact of meteorological factors on PM_2.5 concentration in Changzhou urban areas were analyzed based on observational data of airborne fine particulate matters and meteorological elements near the surface from 2016 to 2018.The results indicated that obvious seasonal variations are observed in PM_2.5 mass concentrations, precipitation, relative humidity, temperature, and other meteorological factors in Changzhou urban areas, with higher values in summer and lower values in winter except for air pressure.PM_2.5 concentrations have a positive correlation with relative humidity, and PM_2.5 exceeding standard rates and its mean concentrations increase with the increase of relative humidity.Precipitation has a scavenging effect on PM_2.5on some degree, which depends on PM_2.5 concentrations before precipitation, precipitation amount and intensity.Larger precipitation amount and intensity usually result in a better scavenging effect on PM_2.5.While the scavenging rate is small when PM_2.5concentration is low before precipitation.PM_2.5 exceeding standard rates and average concentrations are higher in presence of westerly winds than other wind directions.PM_2.5 concentration has a negative correlation with wind speed.PM_2.5 exceeding standard rates and average concentrations decrease with stronger wind speeds.Ground synoptic situations in Changzhou urban areas can be divided into two types.One type is characterized by low air pressure, high temperature, and low PM_2.5 exceeding standard rate and average concentration, and the other type with high air pressure, low temperature, and high PM_2.5 exceeding standard rate and average concentration.

Key words: Meteorological factors, PM_2.5 exceeding standard rate, Scavenging rate, Synoptic situation