兰州地区黑碳和沙尘气溶胶偏振特性观测研究

The aerosol radiative effect is the important issue in the research of climate change and needs to be solved urgently. One of the key work is understanding the radiative properties of aerosol ant its characteristics of spatial distribution and temporal evolution. Lanzhou is located in the arid and semi-arid region of northwest China. In the recent three decades much important progress have been archieved in the research of aerosol radiative properties and its parameterization. While due to the limitation of observation measurement, most research were based on the assumption of spheric shape of aerosol particles, which inevitably will cause calculation error of aerosol radiative effects in a certain degree. And the depolarization lidar provides a powerful mean to improve such defect. This research project is relied on the Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, and the Semi-Arid Climate and Environment Observatoy of Lanzhou University and targeted to the depolarization properties of black carbon and dust aerosol over Lanzhou, China using the most advanced measurements of depolarization lidar, sunphotometer, integrating nephelometer, and aerodynamic particle sizer, which obviously will strengthen the recently started depolarization study in Lanzhou, China by revealing the characteristics of vertical distributions of aerosol depolarization ratio, extinction and scattering coefficient, and the temporal evolution of aerosol optical depth, and calculating the aerosol single scattering albedo, asymmetry factor, and particle effect radius using the T-matrix method to get more information about aerosol particle shape and size. And this research will be helpful to the more accurate calculation of aerosol radiative properties and provide reliable observation basis for the more reasonable and accurate parameterization of aerosol radiative effect.

气溶胶辐射效应是气候变化研究中亟待解决的一个重要问题，而准确理解气溶胶辐射特性及其时空分布特征是其关键之一。兰州地区属于典型的干旱半干旱地区，近三十年来在气溶胶辐射效应和参数化研究方面取得了重要成果。然而观测条件所限，多数研究都基于气溶胶球形粒子假设，不可避免地导致一定误差。偏振激光雷达提供了改进此类不足的手段。本项目依托于兰州大学半干旱气候变化教育部重点实验室和半干旱气候与环境观测站，利用偏振激光雷达、太阳光度计、积分浑浊度仪和尺度谱仪等国际先进仪器，开展目标明确的气溶胶偏振特性研究，揭示兰州地区黑碳和沙尘气溶胶退偏振比、消光和散射系数垂直分布特征和光学厚度时间变化特征，利用T-矩阵方法，计算兰州地区气溶胶单次散射反照率、不对称因子、粒子有效半径等重要参数，掌握气溶胶粒子形状和大小信息，有助于更准确地计算气溶胶辐射特性，为合理确定气溶胶辐射参数化方案提供可靠的观测依据。

气溶胶辐射效应是气候变化研究中亟待解决的一个重要问题，而准确理解气溶胶辐射特性及其时空分布特征是其关键之一。然而观测条件所限，多数研究都基于气溶胶为球形粒子的假设，不可避免地导致一定的误差。本项目主要利用偏振激光雷达等观测仪器，揭示兰州地区气溶胶退偏振比和消光系数的垂直分布特征，并利用T-矩阵方法，分析兰州地区气溶胶纵横比、单次散射反照率、不对称因子、有效半径等的变化特征，以期掌握气溶胶粒子形状和大小信息，为气溶胶辐射参数化方案提供可靠的观测依据。.本项目依托于兰州大学半干旱气候变化教育部重点实验室和半干旱气候与环境观测站（SACOL），综合观测分析和数值模拟，针对项目研究内容，在如下几方面开展了研究工作：.（1）利用微脉冲激光雷达和偏振激光雷达观测资料，分析了兰州地区气溶胶消光系数和退偏振比的垂直分布特征和气溶胶光学厚度的时间演变特征；.（2）利用多角度吸收光度计和太阳光度计观测资料，分析了兰州地区黑碳气溶胶质量浓度和吸收系数的变化特征，以及Ångström指数、有效半径、单次散射反照率、复折射指数实部和虚部等气溶胶光学特性参数的变化特征；.（3）改进了激光雷达信号处理方法中的云识别算法，发展了激光雷达信号降噪方法，提高了激光雷达数据的质量；.（4）利用激光雷达和微波辐射计观测资料，分析了半干旱区卷云的高度、环境温度、几何厚度、光学厚度、消光系数和雷达比等的变化特征；.（5）项目执行期间，共发表SCI论文6篇，资助培养硕士研究生1名，资助在读博士研究生1名，资助在读硕士研究生2名；