宁波地区不同季节不同强度霾天气变化特征

Seasonal characteristics of haze events with different intensity in Ningbo area

利用2014—2016年宁波市镇海地区逐时气象观测资料和大气成分监测资料,对宁波地区霾天气的变化特征进行统计分析。结果表明:2014—2016年宁波地区霾天气小时出现频率为28.8%,湿霾出现频率为61.0%。近3 a宁波地区霾天气小时出现频率呈下降趋势,秋冬季(11月至翌年1月)霾天气小时出现频率较高,夏季(6—8月)霾天气小时出现频率较低;从日变化来看,霾天气小时出现频率峰值集中出现在上午09时和夜间20—23时。宁波地区重度霾的PM_(2.5)、PM_(10)颗粒物浓度为轻微霾的2.13倍和1.92倍,干霾颗粒物浓度高于湿霾,宁波地区霾天气的颗粒物组成较稳定,PM_(2.5)/PM_(10)比重为0.7左右。宁波地区颗粒物浓度与风速和降水量的相关性较好,春季和夏季风速与PM_(2.5)浓度的相关性较高,秋季和冬季风速与PM_(10)浓度的相关性较高;降水与PM_(10)浓度的相关性高于PM_(2.5)浓度。静稳天气时地面风速小易造成细颗粒物浓度的积累增长,冬季西北偏北风和东北风是影响宁波地区PM_(2.5)浓度变化的重要输送路径,当风向为西北风时,冬季和春季PM_(10)浓度增加明显。

Characteristics of haze in Ningbo were analyzed using the hourly meteorological data and concentration of pollutants in Zhenhai from 2014 to 2016.The result shows that the hourly frequency of haze is 28.8%,and the ratio of damp haze is 61.0%.The frequency of haze has decreased during the recent three years.Haze occurred more frequently from November to January and less in summer.The diurnal variation of haze has double peaks which appear at 09：00 and 20：00-23：00 respectively.When the haze is heavy,the particulate concentrations of PM2.5 and PM10 were 2.13 times and 1.92 times as high as those during light haze days.The concentration of particulate matter of dry haze was higher than that of damp haze.The composition of particulate was relatively stable in Ningbo,and the value of PM2.5/PM10 was around 0.7.The correlation of particle concentration with wind speed and precipitation is good.Wind speed and PM2.5 is higher in spring and summer,while PM10 is higher in autumn and winter.The correlation between precipitation and PM10 is higher than PM2.5.The low ground wind speed with stable weather can easily cause an increase in the accumulation of fine particulate matter concentrations.Wind from the northwest and northeast in winter is the main conveying path that results in the change of PM2.5 concentrations in the Ningbo area.When the wind direction changes to the northwest,PM10 concentration in winter and spring will increase significantly.