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

该建议将开发和验证一种程序，利用多光谱、最低点卫星辐射计检索干旱陆地表面上沙漠尘埃的光学厚度。所生成的检索算法也适用于其他相关传感器的数据。利用经过验证的反演技术，利用相关卫星资料估算沙漠地区大气顶部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，从而促进了德意志联邦共和国DFG和摩洛哥王国CNR之间的科学合作协议。1986年10月。全球和国家的沙漠化问题是需要解决的科学问题。(支持Diouri教授和他在Oujda大学的同事是另一项独立提案的主题。DREAMS的成功并不取决于这个提议是否被批准。)被动多光谱星载辐射计气溶胶参数的反演是一个不适定的数学问题。为了在陆地和水面上检索可靠的气溶胶数据产品，需要先验地了解气溶胶和表面光学特性。后者包括气溶胶相函数、单次散射反照率和光谱表面反射率。为了实现这一目标，检索算法通常通过辐射传输建模编译所谓的查找表。本研究项目第一阶段（第1-3年）的科学目标是开发和验证一种检索程序，以获得干旱陆地表面BAER-D上沙漠尘埃的光学厚度。为了实现这一目标，必须承担以下几个具体任务：(1)建立沙尘源区域的光谱表面反射率模型；(2)确定沙漠沙尘的气溶胶光学参数；(3)利用这些气溶胶特性计算查找表以检索气溶胶光学厚度；(4)通过与地面测量结果的比较来验证数据产品。在联合研究计划内计划进行的辐射封闭实验，将包括在地面测量气溶胶光学参数、测定气溶胶的垂直剖面、测定飞机的表面光谱反射率，为发展从卫星数据中提取沙漠沙尘气溶胶的程序提供所有必需的数据。这种程序在世界范围内并不存在。在DREAMS的第二阶段（第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研究沙尘输送，包括研究环流和输送模式的预测能力以及从卫星测量中获取的数据。具体目标是：(1)气溶胶输运的模式预报与卫星测得的AOT沿轨迹区域分布的比较；(2)利用沙漠沙尘AOT的模式预报计算TOA反射率，并与卫星辐射计实测的TOA反射率进行比较；(3)利用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.