环境实际状态气溶胶单次散射反照率垂直分布的机载原位测量研究

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.

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。

气溶胶光学特性的垂直分布特别是气溶胶单次散射反照率的垂直分布特征，对评估气溶胶的直接辐射作用十分关键，但目前关于气溶胶光学特性垂直分布的原位测量还十分缺乏。因此，本项目通过在机载观测平台搭载气溶胶散射、吸收以及亲水性测量仪器，在华北区域开展原位观测研究，为确保数据可信可靠，项目首先基于机载观测建议数据质量控制方法。.本项目通过合理的飞行方案设计，在外场开展了不同污染天气的连续机载气溶胶光学特性垂直分布观测，获得了不同污染阶段气溶胶光学特性垂直分布特征（气溶胶消光系数、单次散射反照率和不对称因子等），探讨基于地面数据去拟合获得垂直分布特征。同时，气溶胶亲水性测试表明，在边界层顶部由于湿度较大对气溶胶单次散射反照率影响较大，可达到10%。.基于原位测量的气溶胶光学特性垂直分布，项目首次验证地基遥感测量方法AERONET在华北地区受人为污染情况下反演准确性问题，发现在污染情况下AERONET反演的AAOD存在10%-20%的高估情况，在短波段高估要更多。同时，利用辐射传输模式研究了不同类型气溶胶光学特性垂直分布，对大气加热率的影响，发现在高空短波吸收性物质的棕碳会对大气稳定度有重要影响。.本项目获得了大量宝贵的机载观测资料，增进了对气溶胶光学特性垂直分布的认识，量化了不同类型气溶胶垂直分布特征对大气加热率的影响，也为气溶胶直接辐射效应提供了有力的技术保障和支撑。

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