摘要
为探究高精度偏振扫描仪(POSP)在偏振交火模式下紫外波段对气溶胶层高(ALH)的探测能力,基于最优估计理论和信息量分析方法,分析了紫外和近紫外波段模拟仿真数据对ALH的灵敏度,并进一步讨论了不同观测组合对ALH信息量和后验误差的影响。研究结果表明:拓展的紫外波段是卫星遥感ALH反演的重要信息源,进一步增加380 nm偏振探测后,ALH的信息自由度(DFS)提高了0.06~0.26,同时后验误差降低了5~30个百分点;联合近紫外410 nm探测信息后,ALH反演后验误差额外降低了7~10个百分点,尤其增加了标高H较低时ALH的反演信息量;观测信息对标高的敏感度随着卫星观测散射角的增大而逐渐降低;粗模态主导的气溶胶、裸土地表相较细模态主导的气溶胶、植被地表来说提供的ALH信息量更少。总体来说,虽然ALH信息量受到气溶胶类型影响表现出了一些差异,但是不同气溶胶类型间ALH信息量受地表类型和偏振测量等的影响通常是相似的。
Objective,As one of the spaceborne detection schemes with the strongest comprehensive aerosol capability at this stage,the polarization crossfire(PCF)strategy has been developed by China.It is composed by the Particulate Observing Scanning Polarimeter(POSP)and the Directional Polarimetric Camera(DPC)together,and has been launched on board the Chinese GaoFen-5(02)and Chinese Atmospheric Environmental Monitoring Satellite(DQ-1),which have been launched in the year of 2021 and 2022.In order to explore the detection ability of the Particulate Observing Scanning Polarization(POSP)based on polarization crossfire in the ultraviolet(UV)band for aerosol layer height(ALH),we focus on the sensitivity study of ALH with the synthetic data in the UV and near-UV wavelength,and further to assess the impact of different conditions on the information content and posterior error of ALH.We hope that our findings can be helpful on the retrieval algorithm development of ALH.Methods Optimal estimation(OE)theory and information content analysis method are employed in this study.OE provides statistical indicators such as averaging kernel matrix and the degree of freedom for signal(DFS),which can represent how much information about the retrieved parameters we can obtain from the satellite measurements.So,combined with the forward simulation of specific satellite sensor observations,information content analysis has been demonstrated to provide support for satellite sensor design and retrieval algorithm development.The advantage is that the retrieval capability can be quantified without invoking the development of true inversion;rather,it provides a top-level physics-based guidance on algorithm design.First,the Unified Linearized Vector Radiative Transfer Model(UNL-VRTM)is used as the forward model to calculate the normalized radiance and polarized radiance at the top of atmosphere(TOA),as well as the Jacobians of TOA results with respective to corresponding parameters.DFS and a posteriori error are introduced to quantity the information content of ALH from the intensity and polarization measurements,respectively.By assuming the different surface types, aerosol models, different typical observation geometry cases, thesensitivity analysis results for different situations can be obtained.Results and Discussions We analyze the the sensitivity of ALH with the scattering anglechange with the solar zenith angle = 40° in this study, the results show that the smaller thescattering angle within 90° to 140° of the satellite observation geometry, the higher thesensitivity of stokes I to scale height H (Fig.10). After that, we choose a fixed observationgeometry to calculate the DFS under different schemes. The research shows that DFS of thebare soil is lower than that of the vegetated surface at 380 nm band (Table 6). Generally, thesurface reflectance has more impact on the information content of H from POSP measurementsthan aerosol optical properties, leading to the lowest information content over bare soil.Meanwhile, with the addition of multi-band measurements and constraints of polarizationinformation, the DFS of the ALH has been significantly improved (Fig.11). By consideringdifferent cases, the addition of intensity and polarization measurements for the retrieval of ALHat 380 nm and 410 nm can improve the H information effectively, the posterior error of theALH retrieval is also reduced by 5%~30% (Fig. 13). It shows that the polarization measurementin UV band has a good constraining effect to the posterior error of H. In addition, with theaddition of intensity and polarization information in the near-UV band at 410 nm, the posteriorerror is additionally reduced by about 7%~10%, the measurements especially improve theinversion of ALH when the H value is low (Fig. 14).Conclusions Firstly, the UV and near-UV bands are the important source of informationcontent for the ALH in satellite remote sensing. Compared with only using intensityobservations at 380 nm, adding the polarization detection at same wavelength band can provideextra 6% to 26% DFS for the retrieval of ALH. Meanwhile, the posterior error is reduced by5%-30%. Secondly, with the combination of near-UV detection information at 410 nm, theposterior error for the retrieval of ALH is additionally reduced by about 7% to 10%, especiallythe retrieval of ALH at low scale height is improved. In addition, the sensitivity of observationinformation to ALH decreases gradually with the increase of the value of correspondingscattering angle when it is in the range from 90° to 140°. Moreover, with coarse-dominatedaerosol, bare soil case will provide less content information of ALH than the fine-dominatedaerosol and vegetation surface;Although ALH information between two types of aerosols showsome distinction because of their different single-scattering optical properties, the dependenceof information on surface types and the impact of polarized measurements generally appearsimilar. The information content analysis results show that the potential capability of POSPinstrument is quite good over various surface types, aerosol models, based on the use ofSpaceborne Polarization Crossfire strategy.
作者
顾浩然
李正强
侯伟真
刘振海
伽丽丽
李殷娜
郑杨
史正
许华
洪津
麻金继
陈震霆
Gu Haoran;Li Zhengqiang;Hou Weizhen;Liu Zhenhai;Qie Lili;Li Yinna;Zheng Yang;Shi Zheng;Xu Hua;Hong Jin;Ma Jinji;Chen Zhenting(College of Geography and Tourism,Anhui Normal University,Wuhu 241000,China;Aerospace Information Research Institute,Chinese Academy of Sciences,Beijing 100101,China;University of Chinese Academy of Sciences,Beijing 100049,China;Anhui Institute of Optics and Fine Mechanics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,Anhui,China;School of Information Engineering,Kunming University,Kunming 650214,Yunnan,China)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2023年第6期55-71,共17页
Acta Optica Sinica
基金
国家杰出青年科学基金(41925019)
国家自然科学基金(41871269,42175148)
云南省地方联合基金(202001BA070001-090)
云南省李正强专家工作站(202205AF150031)。
关键词
大气光学
偏振扫描仪
气溶胶层高
偏振遥感
信息量分析
scanning polarimeter
aerosol layer height
polarimetric remote sensing
information content analysis
