Determination of optical properties of desert dust aerosol for satellite validation - AERVAL

该建议将制定和验证一种程序，利用多光谱、天底观测卫星辐射计，反演干旱土地表面沙漠尘埃的光学厚度。所产生的检索算法也将适用于从其他相关传感器的数据的应用。利用已验证的反演技术，利用相关卫星资料估算沙漠地区大气层顶气溶胶光学厚度的区域分布。该项目建立了德国和摩洛哥科学家之间的合作，从而有助于德国联邦政府和摩洛哥王国CNR之间的科学合作协议。1986年10月全球和国家的荒漠化问题是需要解决的科学问题。（支持M教授）Diouri和他在乌季达大学的同事是一个单独和独立的建议的主题。梦想的成功并不取决于这个提议是否被批准。）利用被动多光谱辐射计反演气溶胶参数是一个不适定的数学问题。要检索可靠的气溶胶数据产品在陆地和水面，气溶胶和表面光学特性的先验知识是必需的。后者包括气溶胶相函数、单次散射谱和光谱表面反射率。为了实现这一目标，反演算法通常通过辐射传输建模来编译所谓的查找表。该研究项目第一阶段（1-3年）的科学目标是开发和验证一种检索程序，以得出干旱土地表面沙漠尘埃的光学厚度BAER-D。为实现这一目标，必须开展以下几项具体任务：（1）建立沙尘源区表面光谱反射率模式;（2）确定沙尘气溶胶光学参数;（3）利用这些气溶胶特性计算查找表，反演气溶胶光学厚度;（4）通过与地面测量数据的比较来验证数据产品。计划在联合研究项目范围内进行的辐射闭合实验将包括对浮质光学参数进行地面测量，确定浮质的垂直分布，确定飞机表面的光谱反射率，从而为开发利用卫星数据对沙漠尘埃进行浮质反演的程序提供所有必要的数据。这种程序在世界范围内并不存在。在DREAMS的第二阶段（4-6年），计划将BAER-D检索程序应用于卫星数据。整个项目第二阶段的主要目标是以尘埃输送为重点，包括调查环流和输送模型的预测能力以及从卫星测量中检索的数据。具体目标是：（1）模式预测的气溶胶输送与卫星沿着轨迹反演的AOT区域分布的比较;（2）模式预测的沙漠沙尘AOT的TOA反射率的计算与卫星辐射计测量的TOA反射率的比较;（3）由TOA反射率估算上升流短波TOA通量。

This proposal will develop and validate a procedure for the retrieval of optical thickness of desert dust over arid land surfaces using multi-spectral, nadir-looking satellite radiometers. The retrieval algorithms generated will also be suitable for application to data from other relevant sensors. Using the validated inversion technique, the regional distribution of Top Of the Atmosphere (TOA) aerosol optical thickness (AOT) over desert regions will be estimated from relevant satellite data. The project establishes collaboration between scientists from Germany and Morocco and thereby contributes to the agreement on scientific cooperation between the DFG of the Bundesrepublik Deutschland and the CNR of the Kingdom of Morocco from 28. Oct. 1986. The global and national problem of desertification is the scientific issue to be addressed. (Support for Prof. M. Diouri and his co-workers at the University of Oujda is the subject of a separate and independent proposal. The success of DREAMS does not depend on this proposal being granted.) The retrieval of aerosol parameters from passive multi-spectral space-borne radiometers is an ill-posed mathematical problem. To retrieve reliable aerosol data products over land and water surfaces, a-priori knowledge of the aerosol and surface optical properties are required. The latter comprise the aerosol phase function, the single scattering albedo and the spectral surface reflectance. To achieve this objective retrieval algorithms typically compile so-called Look Up Tables by radiative transfer modeling. The scientific objective of this research project in its first phase (year 1-3) is the development and validation of a retrieval procedure to derive the optical thickness of desert dust over arid land surfaces BAER-D. To achieve this goal several specific tasks have to be undertaken: (1) The development of a model of spectral surface reflectance of dust source regions, (2) The determination of optical aerosol parameters for desert dust, (3) The calculation of look-up-tables using these aerosol properties for the retrieval of the aerosol optical thickness, (4) The validation of the data products by comparison with ground based measurements. The radiation closure experiment, planned within the joint research project, which will include ground-based measurements of aerosol optical parameters, the determination of vertical profile of the aerosol, the determination of the surface spectral reflectance from aircraft provides all required data for the development of the aerosol retrieval procedure for desert dust from satellite data. Such a procedure does not exist worldwide. In phase 2, (year 4-6) of DREAMS, applications of the BAER-D retrieval procedure to satellite data are planned. The main aim of the second phase within the overall project, which has a focus on dust transport, comprises the investigation of the predictive power of circulation and transport models and data retrieved from satellite measurements. The specific objectives are: (1) The comparison of model predictions of the transport of aerosol with regional distributions of AOT retrieved from satellite measurement along the trajectories, (2) The calculation of TOA-reflectance from model predictions of the AOT of desert dust and comparison with measured TOA reflectances of the satellite radiometers, (3) The estimation of the up-welling shortwave TOA-flux from TOA reflectances.