6S Radiative Transfer Model Research Articles

Aerosol optical thickness retrieval over the Atlantic Ocean using GOES imager data

An algorithm based on simulated satellite signal calculated by the 6S radiative transfer model has been developed in order to retrieve the aerosol optical thickness of dust over the Atlantic ocean. The algorithm is applied to the visible channel of Geostationary Operational Environmental Satellite (GOES 8) images. The inversion uses a look-up table giving the satellite signal intensity as a function of surface albedo, viewing geometry, solar illumination and the optical properties of the aerosols. The study consists of assessing the feasibility of monitoring and mapping the transport of suspended particles across the Atlantic from the Sahara to the Caribbean. The study area is between 10 and 25 N and 30 and 65 W. The optical thickness of aerosols has been calculated over a period of 11 days between 10th and 20th of June 1997 for the 14:15 UT GOES image acquisition. The calculated aerosol optical thickness ranges from 0.0 to 0.81 with an important event of dust presence occurring between 13th and 16th of June. The retrieved aerosol optical thickness is in good agreement with the values obtained between 14h UT and 15h UT from ground based sun photometer measurements on the island of Guadeloupe, and a coefficient correlation ( R 2) of 0.88 has been found between the data sets.

Comparison of AVHRR-derived and in situ surface albedo over the greenland ice sheet

This paper discusses a methodology for computing the clear-sky surface albedo over the Greenland ice sheet by using advanced very high resolution radiometer (AVHRR) global area coverage visible and near-infrared reflectances. This approach is then used to map the monthly changes in albedo over the entire Greenland ice sheet during the spring and .summer months. The methodology includes corrections for the intervening atmosphere by using the 6S radiative transfer model. Additional corrections for the anisotropic nature o f snow reflectance and the conversion from a. marrow- into a broadband albedo are made based on in .site measurements from the Swiss Federal Institute of Technology/University of Colorado camp at 69°34′N, 49°18′W Comparison with surface albedo field ineasureinents indicates that before the onset of snoic melt, agreement is good between the satellite-derived and measured surface albedo. After melt begins, it is difficult to compare the satellite values with the field data owing to melt water ponding on the ice sheet surface. With appropriate modifications, the 6S radiative transfer model is suitable for atmospherically correcting AVHRR visible and near-infrared radiances atmospherically polar regions.