Improvement of cloud's spectral reflection simulation using MODIS cloud products

A method calibrating visible channels using deep convective cloud targets has been developed. Deep convective clouds reflect most of sunlight, thus atmospheric and surface effects on the TOA solar radiation can be minimized. This provides a possibility of estimating reflected radiances with a reasonable accuracy without a priori information on atmosphere and surface properties. Reflectance for the MODIS 0.645 µm solar channel is calculated using a radiative transfer model (RTM) with several cloud parameters as inputs. In order to examine the possibility of using this approach to calibrate other satellites (for example, Meteosat-8 or Korean satellite COMS) the calculated reflectance is compared with the MODIS measurements. MODIS derived cloud properties are used for the inputs to the RTM. Carefully selecting horizontally homogeneous and optically thick cloud pixels, reflectances of cloud targets are calculated. Sensitivity tests show that cloud optical thickness is the most important parameter to determine the reflectance while results are less sensitive to chosen effective radius. Initial results indicate that the method may be used within ±10% error for the calibration of the solar channel.