Search results for "Diffuse sky radiation"
showing 5 items of 15 documents
The Elliptical Polarization of Light Scattered by a Volume of Atmospheric Air
2010
The scattering of linearly polarized light by aerosol particles produces partly polarized light whose ellipticity is theoretically and experimentally investigated for the specific case of a continental atmospheric aerosol in a volume of air. With the Mie theory and under the assumption of various aerosol size-distribution models, the ellipticity has been computed as a function of the scattering angle for various wavelengths. The computations have been based upon complex indices of refraction: M = 1.5-0.0i, M = 1.5-0.0li, M = 1.5-0.li, M = 1.44-0.0i, M = 1.4-0.0i, M = 1.33-0.0i. The comparison between computed and measured values for the wavelengths of lambda = 0.45 micro to lambda = 0.65 mi…
Sky radiation, polarization and twilight radiation in Greenland
1966
A) The measurements of the spectral radiances in the solar almucantar (scattering function) and the degree of polarization of the skylight in Greenland indicate the following: 1) The air near the surface of the ice cap of Northern Greenland is very pure. 2) The sky radiance however is different from the pure molecular (Rayleigh) atmosphere, the measured scattering function does not followRayleigh's law. 3) On the other hand the measured scattering functions cannot be explained satisfactoryly by scattering on the aerosols which have been measured near the surface. 4) Therefore the presence of a few particles per cm3 with radii in the range 0.10≤r≤1μ in heigher atmospheric layers has to be po…
Influence of Multiple Scattering of the Intensity and Polarization of Diffuse Sky Radiation
1964
A physical explanation of the intensity and polarization of diffusion skylight in the plane of the sun’s vertical is attempted by an approximation method which takes into account the effects of multiple scattering. Various model atmospheres are considered. The scattered radiation field is assumed to be composed of (1) the scattered radiation due to the molecular atmosphere resulting from all orders of scattering; (2) the scattered radiation due to the turbid atmosphere including primary scattering only; and (3) the scattered radiation due to the turbid atmosphere resulting from secondary and higher-order scattering. The contribution due to the first term can be computed from the tables appl…
Vicarious calibration of MERIS over dark waters in the near infrared
2005
Abstract We propose to evaluate the calibration of MERIS (MEdium Resolution Imaging Spectrometer) over dark waters in the near infrared. We work with 5 months of data, from July to November 2003, over five world sites: Venice and Lampedusa in Italy, El Arenosillo in Spain, MOBY/Lanai and CalCOFI/San Nicolas in the United States. The sites are all equipped with a CIMEL station that forms part of the AERONET network. The basic idea is to associate CIMEL sky radiance measurements with MERIS level-1b data in a twin geometry which corresponds to the same scattering angle. This vicarious calibration relies on an accurate description of the atmospheric scattering based on the CIMEL measurements. A…
Spectral calibration of hyperspectral imagery using atmospheric absorption features
2006
One of the initial steps in the preprocessing of remote sensing data is the atmospheric correction of the at-sensor radiance images, i.e., radiances recorded at the sensor aperture. Apart from the accuracy in the estimation of the concentrations of the main atmospheric species, the retrieved surface reflectance is also influenced by the spectral calibration of the sensor, especially in those wavelengths mostly affected by gaseous absorptions. In particular, errors in the surface reflectance appear when a systematic shift in the nominal channel positions occurs. A method to assess the spectral calibration of hyperspectral imaging spectrometers from the acquired imagery is presented in this p…