Wednesday, 17 January 2007: 9:15 AM
Simulating MODIS solar channels under cloudy condition using newly developed fast radiative transfer model
210B (Henry B. Gonzalez Convention Center)
A solar-band fast radiative transfer model (SFRTM-1), appropriate for application to single-layered cloudy conditions, has been being developed for simulating outgoing bi-directional reflectance at the top of the atmosphere for the MODIS solar channels. The model accepts the well known adding method to evaluate total reflectance at all possible satellite zenith angles for any solar zenith and azimuth angles. Cloud parameters such as the bi-directional reflectance function (BDRF), downward spherical reflectance, and cloud transmittance, are pre-computed and tabulated into lookup tables for each specific MODIS channel. To select the specific cloud parameters from the database, SFRTM-1 employed a 5-D, 3-D, and 2-D interpolation scheme, which is based mainly on a polynomial interpolation technique. A fast clear sky radiative transfer model (subroutine of SFRTM-1) is under development. This clear sky model will provide cloud-free optical thicknesses for the SFRTM-1. Comparisons with DISORT computations will be discussed. Preliminary simulations of MODIS observations based on the MODIS cloud products will also be shown.