气溶胶单次散射反照率因子可以反应气溶胶对光散射和吸收的强弱，是评价气溶胶辐射强迫效应的重要的因素。其垂直分布对天气和气候都有重要的影响，但目前关于气溶胶单次散射反照率垂直分布的观测还非常少，仅有的垂直观测也是“干”状态（RH<40%）单次散射反照率的观测，而气溶胶单次散射反照率由以下三个因素决定：气溶胶的散射系数、气溶胶的吸收系数和亲水性增长。已有探测不能反应实际气溶胶单次散射反照率的变化。.本项目通过机载观测的方式，研究北京地区环境状态气溶胶单次散射反照率的变化特征。基于气溶胶散射系数、气溶胶吸收系数、亲水性增长测量设备的垂直观测，分析这三个因素对单次散射反照率的影响。并通过和机载测量粒径谱仪的光学闭合实验，保证观测数据的质量。本项目的垂直观测结果可以验证北京地区的AERONET反演产品，和计算大气加热率。通过大量的飞行数据，给出单次散射反照率的参数化方案，为模式模拟提供宝贵的资料。

Aerosol single scattering albedo (SSA) is an indicator of the scattering and absorption properties of aerosol in the atmosphere, which is a primary determinant of aerosol direct radiative forcing. The vertical distribution of SSA was thought to be of critically important to regional weather and climate. However, only limited in-situ observation of SSA was conducted to improve our understanding of its effect on aerosol direct radiative forcing. The limitation of the in-situ SSA vertical distribution conducted before was that the aerosol was dry to RH < 40% before measured, which could not reflected the real characteristic of aerosol in the atmosphere, as SSA was influenced by aerosol scattering coefficient, aerosol absorption coefficient, and hygroscopic growth factor. The uncertainty of vertical distribution of SSA prevent determination of the effect of the aerosol on climate..Here in this project, we intend to observe the vertical characteristic of aerosol scattering coefficients, aerosol absorption coefficients, and the hygroscopic growth factor using a comprehensive aerosol observation aircraft in Beijing. The vertical distribution of ambient SSA will for the first time be measured in North China Plain (NCP).Closure studies will be done between the aerosol optical properties and aerosol size distribution measured simultaneously, in order to prove the high quality of the measured vertical SSA data. The effect of relative humidity (RH) on the vertical distribution of SSA will also analyzed, and the performance of AERONET retrievals AAOD will evaluated by the comparison with the in-situ observed vertical profiles in the NCP. The integrated vertical extinction coefficients will compared with AOD observed by AERONET, and the integrated vertical SSA will be used to evaluate the AAOD retrieval from the AERONET when the AOD > 0.4 at 440 nm. The results of this project can be used to improve the retrievals of ground based or satellite remote method, which will also help in accurately evaluate the role of aerosol direct effect in climate change.