Retrieval of atmospheric properties and surface bidirectional reflectances over land from POLDER/ADEOS

Abstract

Abstract. Polarization and Directionality of the Earth's Reflectances (POLDER) is a new instrument devoted to the global observation of the polarization and directionality of solar radiation reflected by the Earth-atmosphere system. It will fly onboard the ADEOS platform in 1996. This paper outlines the improvements expected from POLDER in the description of atmospheric aerosols and water vapor over land, and of surface bidirectional reflectances. It then gives a detailed description of the operational algorithms which are implemented in the "land surface and atmosphere over land" processing line. This line is part of an effort initiated by Centre National d'Etudes Spatiales (the French Space Agency) to develop lines of products in order to facilitate the exploration of POLDER's new capabilities by the international science community. Emphasis is given in this paper to the presentation of the principles, physical rationale, and elements of validation of the algorithms of this processing line. The main products are (1) for each orbit segment, the amount and type of aerosols, the water vapor content, and bidirectional reflectances corrected for atmospheric effects, and (2) every 10 days, global maps of surface directional signatures, of hemispherical surface reflectances, and of parameters describing the statistical distribution of aerosol and water vapor content. These products will be made available to all interested investigators. The most innovative algorithms of the processing line are (1) cloud detection, based on a series of tests involving reflectance thresholds, oxygen pressure estimates, and analysis of polarized radiance in the rainbow direction, (2) retrieval of aerosol optical thickness and type from directional polarized radiance measurements, and (3) retrieval of surface directional signature through an adjustment of a time series of directional reflectance measurements with a semiempirical bidirectional reflectance model. IntroductionBefore the end of the century, a series of Earth-orbiting satellites will carry several advanced, well-calibrated instruments designed to provide global observations of the Earth's oceans, land, and atmosphere.

The use of remote sensing in light use efficiency based models of gross primary production: A review of current status and future requirements

“…Our understanding of bidirectional reflectance, radiative transfer modeling, and interactions between reflectance and forest stand structure has benefited greatly from multi-angle instruments, including the POLDER (Polarization and Directionality of Earth Reflectance) (Deschamps et al, 1994) and MISR (Multi-angle Imaging Spectrometer) (e.g. Lyapustin et al, 2007) sensors, specifically designed to address BRDF characteristics of the Earth surface from space (Leroy et al 1997;Gamon et al, 2006).…”

Global products of vegetation leaf area and fraction absorbed PAR from year one of MODIS data

“…Example algorithm runs with multi-spectral, multi-angle data over Africa from the POLDER instrument (Leroy et al, 1997), assuming a mean overall uncertainty of 20%, were performed. The LAI saturation frequency decreases with an increase in the number of view angles (Table 3).…”

Impact of cloud horizontal inhomogeneity and directional sampling on the retrieval of cloud droplet size by the POLDER instrument

“…When it passes over a target, the POLDER instrument acquires up to 16 successive multi-angle measurements of both the total and polarized reflected solar radiance in nine narrow channels with center wavelengths of 443,490,565,670,763,765,865,910, and 1020 nm. For three of the nine spectral bands (490, 670, and 865 nm), a polarizer is added to the filters to assess the degree of linear polarization and the polarization direction, which are related to the I , Q, and U Stokes vectors of the polarization (Leroy et al, 1997).…”