华北中部夏季气溶胶和云分布特征

气溶胶与云的垂直分布特征是气溶胶间接气候效应关注的重点。基于2018年7—8月华北中部6架次飞机观测数据,研究气溶胶和云滴的垂直和水平分布特征。结果表明:华北中部780~5687 m高度内气溶胶数浓度( N_a )平均值为821.36 cm-3,最大量级可达到104 cm-3,云中气溶胶数浓度(N_acc)占总颗粒浓度的80%以上,表明细颗粒占大多数,气溶胶粒子算术平均直径( D_m )平均值为0.12~0.52 μm；大气层结对气溶胶垂直分布影响较大,逆温阻挡气溶胶垂直输送,高空(高度2000 m以上) D_m 的垂直分布受到相对湿度影响较大； N_a 和 D_m 在垂直方向波动较大,水平方向波动较小；低层云中云滴数浓度(N_c)较大、液态水含量(L)较小,而中层和高层云中N_c较小、L较大,N_c和云滴有效半径(R_e)的概率密度函数均为双峰型分布,L的概率密度函数为单峰型分布；气溶胶数浓度谱基本呈现多峰型分布,而云滴数浓度谱多呈现单峰型分布。

Characteristics of Aerosol and Cloud over the Central Plain of North China in Summer

The vertical distribution of aerosols and clouds is a key issue in the indirect climate effects of aerosols. Based on the aerosol and cloud droplet number concentration data observed by 6 aircrafts over the central plain of North China from July to August in 2018, the vertical distribution and spectral characteristics of aerosols and clouds are studied. The results show that the mean value of aerosol number concentration ( N_a ) of this area is higher than that in Central China, the in-cloud aerosol number concentration (N_acc) accounts for over 80% of the total concentration, and the mean particle diameter ( D_m ) is between 0.12 and 0.52 μm, which means fine particles contribute the largest proportion. The aerosol number concentration decreases with the height. The total aerosol number concentration is higher with middle and high stratus comparing to low-level stratus. The vertical distribution of N_a is significantly affected by atmospheric stratification, as inversion temperature layer block the vertical transport of aerosols. The vertical distribution of mean diameter below 3500 m is relatively stable, with an average of 0.23 μm, while increases with the height above 3500 m. The vertical distribution of aerosol particle mean diameter at high altitude (above 2000 m) is greatly affected by relative humidity. Compared with the vertical distribution of aerosol number concentration and mean diameter, the horizontal variety is smaller. In low-level stratus, the cloud droplet number concentration (N_c) is large, and the liquid water content (L) is small. In middle and high stratus, the cloud droplet number concentration is small, and the liquid water content is large. The probability distribution function of cloud droplet number concentration and liquid water content are bimodal distribution, and the probability distribution function of cloud droplet effective radius (R_e) show a single mode. The distribution of aerosol number concentration spectrum shows multi-peak distribution, and the average aerosol spectrum show three-peak distribution. The distribution of cloud droplet number concentration spectrum shows a single peak, which appears at the scale of 9-16 μm, and the spectral width of cloud droplets is 50 μm. The parameter characteristics of aerosol spectral distribution obtained by fitting aerosol spectral distribution can provide an important in situ measurement basis for improving the parameterized schemes such as regional climate model and aerosol-cloud model.