Estimation of Broadband top-of-atmosphere and Surface Long Wave Radiation from MODIS

NASA-operated Clouds and Earth's Radiant Energy System (CERES) is the only instrument on board the EOS platform providing broadband measurements of top-of-atmosphere (TOA) and parameterized surface radiative fluxes in both the shortwave and long wave (LW) spectral regions. However, the CERES scanner's nadir footprint resolution of 20 km has been found to be insufficient to resolve small targets such as small-scale fire plumes, estimating net surface radiative fluxes required at finer spatial scale for hydrological applications, etc. In this study an empirical scheme is developed to utilize the high spatial resolution (1 km) spectral imagery of Moderate Resolution Spectral Radiometer (MODIS) to derive broadband LW irradiance at TOA. The MODIS-CERES comparisons of broadband LW irradiance yield TOA flux estimates with a small RMS error of less than 5 W m-2 under all sky conditions. These TOA LW flux estimates will be employed in a simplified version of the CERES sub-system TOA-to-surface parameterizations to produce surface LW fluxes. Comparison with ground truth at several surface stations will be presented.