航空偏振遥感数据反演陆地上空气溶胶光学厚度

在陆地上空气溶胶遥感中，地表多样性会导致地表反射率计算误差增加，降低地气解耦精度，进而影响气溶胶反演精度。多角度、多光谱和偏振观测数据的引入有利于解决地气解耦精度和气溶胶参数的提取精度受限的问题。基于多角度偏振辐射计(AMPR)航空多光谱遥感数据，结合气溶胶散射和地表偏振反射规律，提出了在1 640 nm波段对AMPR观测偏振反射率进行连续大气辐射校正，实现地气解耦的方法。在此基础上，构建了陆地上空气溶胶偏振反演算法。运算过程中使用665和865 nm波段观测数据进行气溶胶参数提取，使用1 640 nm波段观测数据结合提取的气溶胶参数进行大气偏振辐射校正，重新获取地表偏振反射率。在反演过程中引入迭代，逐步逼近大气与地表真实辐射值，实现地气解耦，并利用查找表的方法实现气溶胶光学厚度反演。通过AMPR在京津唐地区5个架次的航空观测实验数据对反演算法进行了验证，结果与地基CE318观测数据一致性较好，在气溶胶光学厚度小于0.5的情况下，反演平均误差为约0.03。

Inversion of Aerosol Optical Depth over Land Surface from Airborne Polarimetric Measurements

The diversity of land surfaceleads to an increase of the uncertainty in surface reflectance calculation, whichreduces theaccuracy of land-atmospheric decoupling, and then of the aerosol retrieval. The multi-spectral, multi-angle and polarized information, which can be provided by the Atmosphere Multi-angle Polarization Radiometer (AMPR), is helpful to solve the problem. The behavior of aerosol scattering amongdifferent wavelengths is smooth. At the same time the land surface polarized reflectance does not show any dependence in the measurement bands. Based on these conclusions, we developed a method to separate land surface and atmosphericradiation by successive atmospheric correction. Further on, the aerosol retrieval algorithm was build. In the algorithm, the aerosol optical thickness was retrieved at 665 and 865 nm, while thesurface polarized reflectance was reobtained at 1 640 nm by atmospheric correction. The atmospheric correction (1 640 nm) and aerosol retrieval (665 and 865 nm) form a cycle. Then, an iteration method was employed and it approaches to the real radiant values of atmosphere and land surface step by step. At last, we retrieved aerosol optical depth from a look-up table which was builtby 6 fine and 6 coarseaerosol modes. The AMPR have performedat least 5 flights mission over Beijing, Tianjin and Tangshan region. Data of theseobservations were used to verify the algorithm and it was found that the AOD retrieved from AMPR and CE318 have good coherence. When the AOD is lower than 0.5, the average deviation is below 0.03.