团簇自然气溶胶散射相函数的数值分析

针对不同比例的灰尘和海盐团簇自然气溶胶，利用离散偶极子近似(DDA)法，通过考察成分的影响，使用波长为0.55 m，尺度参数变化范围为0.1~25时，研究了散射相函数和激光雷达比的影响，结果表明二者的变化趋势大体相同。尺度参数为13~24时，团簇自然气溶胶散射相函数有明显的后向散射加强，其中尺度参数为18附近，后向散射加强效应最明显。灰尘比海盐对散射相函数影响更大，二者的影响主要集中在尺度参数为15~25范围内，但除了散射角为180附近的后向外，影响的散射角方向略有不同。不同比例下的团簇自然气溶胶激光雷达比在尺度参数为3左右有最大值，其值约为180。在尺度参数为0.2~25范围内，成分对激光雷达比的影响不大，相对偏差小于10%，特别是尺度参数为0.5~2时的影响可以忽略，相对偏差小于1%。

Numerical analysis of scattering phase function for natural aerosol aggregates

Scattering phase functions and lidar ratios of natural aerosol aggregates at different ratios of dust and sea-salt were carried out based on discrete dipole approximation (DDA) for the size parameters from 0.1 to 25. Curves of scattering phase function and lidar ratio for natural aerosol aggregates as a function of scattering angle were almost the same. Scattering phase functions had distinct opposition effect for the size parameters from 13 to 24, which was most evident around the size parameter of 18. The effect of increasing dust on scattering phase function of natural aerosol aggregates were greater than that of increasing sea-salt, and the main influence range of the size parameter was from 15 to 25. These effects were distinct at different scattering angle except for the backscattering with the scattering angles around 180°. The lidar ratios of natural aerosol aggregates had the maximum value of about 180 around the size parameter of 3. Influences of composition variations on lidar ratios were not large for the size parameters from 0.2 to 25, especially for the size parameters from 0.5 to 2 with the differences less than 1%.