气象因素对常州市区PM2.5浓度影响

利用2016—2018年常州市区环境空气细颗粒物数据，结合同期地面气象资料，分析了常州市区PM_2.5以及气象因素的变化特征，并统计分析气象因素对PM_2.5浓度的影响。结果表明：常州市区PM_2.5、降水量、相对湿度和气温等具有明显季节性，呈夏季较高冬季较低，而气压夏季较低冬季较高的特征。相对湿度与PM_2.5呈正相关，即随着相对湿度的增加PM_2.5超标率和平均浓度均增加；降水对PM_2.5具有一定的清除作用，清除率与降水前PM_2.5浓度、降水量、降水强度有关，降水量、降水强度越大，则降水清除效果越好，而降水前PM_2.5浓度较小，则清除率不明显；常州市区偏西风时PM_2.5的超标率和平均浓度较其他风向较高；风速对常州市区PM_2.5的影响呈负相关，即风速越大PM_2.5超标率和平均浓度均减小；常州市区地面天气形势可以分为两种类型，第一种类型表现为气压较低气温较高，PM_2.5超标率以及平均浓度相对较低，而第二种类型表现为气压较高气温较低，PM_2.5超标率以及平均浓度相对较高。

Impacts of meteorological factors on PM2.5 concentration in urban regions of Changzhou

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.