Parameterization of aerosol number concentration distributions from aircraft measurements in the lower troposphere over Northern China

To obtain representative models of aerosol size distributions in the vertical dimension, we performed an extensive investigation on aerosol number concentration distributions from 0.1 µm to 3.0 µm based on airborne aerosol measurements, which were measured by a PCASP-100X on 33 flights over Northern China. A multi-modal lognormal size distribution with a base 10 logarithm is applied to fit the measured aerosol size distributions at different altitudes. Most of them can be fitted well by using a tri-modal distribution, while some of the data need to be fitted using a four-mode distribution. As the height increases, the aerosol distributions gradually become monotonous and display double-peak or single-peak lognormal distributions. Vertical variations in aerosol distributions over four days were analyzed and compared to each other. Statistical parameters of aerosol size distributions in the vertical dimension were obtained and analyzed. Relatively stable modal parameters from the ground to a height of 7 km were found for modes 1 and 2. The first and second peaks in the aerosol distributions were found from 0.08 µm to 1.2 µm and from 0.12 µm to 0.4 µm, and their medians were approximately 0.1 µm and 0.3 µm. The standard deviation did not change very much, from 0.05 µm to 0.6 µm and from 0.2 µm to 0.6 µm. The mean particle sizes in modes 1 and 2 were similar and showed an exponential decline with increasing height. Typical modal distributions of aerosol concentrations ranging in size from 0.1 µm to 3.0 µm over the vertical dimension in Northern China are presented along with statistical data. The parameterized formula is also provided in this paper.