新疆天山夏季气象条件对气溶胶粒径分布的影响

Impact of meteorological elements on size distributions of aerosol in summer at the Mountain Tianshan in Xinjiang

使用宽范围粒径谱仪对天山白杨沟风景区2019年8月5-25日10 nm^10μm气溶胶数浓度粒径分布进行观测,结合气象要素数据,分析了天山地区夏季气象条件对气溶胶粒径分布特征的影响.结果表明,夏季天山地区10 nm^10μm气溶胶数浓度、表面积浓度和体积浓度平均为3539.2 cm^-3、116.5μm^2·cm^-3和17.6μm^3·cm^-3.不同降水过程对气溶胶数浓度的影响不同.不同降水过程中气溶胶数浓度谱均为单峰型分布,持续时间长的小雨和毛毛雨对气溶胶数浓度谱谱形的影响较小,而降雨量较强的短时降水过程往往会使得气溶胶粒径谱峰值往大粒径段偏移.降雨过程气溶胶表面积浓度谱和体积浓度谱为多峰型分布,表面积浓度主要集中在30~500 nm的细粒子段,体积浓度主要集中在1~10μm的粗粒子段.相对湿度(RH)对核模态气溶胶数浓度和积聚模态气溶胶数浓度的影响较大,对爱根核模态气溶胶数浓度的影响较小.不同相对湿度条件下气溶胶数浓度谱均为单峰型分布.随着相对湿度的增加,气溶胶数浓度谱的峰宽呈现先增加后减小的趋势,这种变化趋势在<40 nm时更加显著.气溶胶数浓度、表面积浓度和体积浓度随风速风向的分布与能见度随风速风向的分布呈现相反的趋势.

In this study,the size distribution of aerosol number concentration(10 nm^10μm)and meteorological data were collected from August 5 to 25,2019 at the Mountain Tianshan by using a wide⁃range particle spectrometer(WPS)and an automatic weather station.Consequently,the characteristic of the aerosol size distribution and their impacts by meteorological elements were analyzed.The results indicated that the average number concentration,surface area concentration and volume concentration at Mountain Tianshan were 3539.2 cm^-3,116.5μm^2·cm^-3 and 17.6μm^3·cm^-3,respectively.Precipitation processes had distinct influences on the aerosol number concentration.In different precipitation processes,the spectra distribution of aerosol number concentration was unimodal.Light rain and drizzle rain with long duration time had little influence on the spectrum shape of aerosol number concentration,while strong precipitation with short⁃time made the peak of number concentration shift to a larger size segment.The spectra of aerosol surface area concentration and volume concentration were multimodal during different precipitation processes,mainly concentrated in the fine particle segment of 30~500 nm,and in the coarse particle segment of 1~10μm,respectively.Relative humidity(RH)had greater influences on the number concentration of nucleation mode and accumulate mode than the Aitken mode.The spectra of number concentration were unimodal under different RH.With the enhancement of RH values,the peak width of number spectrum increased first and then decreased,which was more significant in the size smaller than 40nm.The distributions of aerosol number concentration,surface area concentration and volume concentration with wind speed and wind direction were opposite to that of visibility.