北京地区夏冬季气溶胶变化特征分析

北京市夏季平均可吸入颗粒物质量浓度(ρ(PM₁₀))和气溶胶粒子数密度的平均日变化呈现明显的双峰结构,冬季除12:30—15:00相对较小外,其余时间都很大;夏季大气能见度的平均日变化呈单峰结构,而冬季呈双峰结构;夏季平均PM₁₀和气溶胶粒子数密度通常比冬季的小;北京市夏季平均大气能见度比冬季的小,主要原因在于夏季空气相对湿度大,半径大于1 25μm的大粒子数密度较大,夏冬季0:00—9:00各时刻的平均能见度存在较大差别,其余时间的差别不大。 

Variation of Aerosol Parameters in the Summer and Winter in Beijing

It is found that there are two peaks for the average diurnal variations of PM₁₀ and NOPC in the summer in Beijing, and an obvious valley can be seen between 12:30 to 15:00 for their average diurnal variation in the winter. There is one single peak for the average diurnal variation of atmospheric visibility in the summer, while there are two peaks in the winter. PM₁₀ and NOPC are usually lower in the summer than in the winter. The average visibility is much lower during 0:00 to 9:00 in the summer than in the winter, because of the very high relative humidity and higher number concentration of large particles (i.e. r>1^25 μm) in the summer during the period.