Fusion of CERES, MISR, and MODIS measurements for top-of-atmosphere radiative flux validation

The Clouds and the Earth's Radiant Energy System ( CERES), Multiangle Imaging Spectroradiometer ( MISR), and Moderate- resolution Imaging Spectroradiometer ( MODIS) instruments aboard the Terra satellite make critical measurements of cloud and aerosol properties and their effects on the Earth's radiation budget. In this study, a new multiangle, multichannel data set that combines measurements from all three instruments is created to assess uncertainties in instantaneous shortwave ( SW) top- of- atmosphere ( TOA) radiative fluxes inferred from CERES Angular Distribution Models ( ADMs). MISR Level 1B2 ellipsoid- projected radiances from nine viewing directions in four spectral bands are merged with CERES by convolving the MISR radiances with the CERES Point Spread Function. The merged CERES- MISR data are then combined with the CERES Single Scanner Footprint TOA/ Surface Fluxes and Clouds ( SSF) product to produce the first merged CERES- MISR- MODIS data set. CERES and MISR data are used to generate narrow- to- broadband regression coefficients to convert narrowband MISR radiances to broadband SW radiances as a function of MODIS- based scene type. The regression uncertainty for all- sky conditions over ocean is approximately 4%. Up to nine SW TOA fluxes for every CERES footprint are estimated by applying the CERES Terra ADMs to each MISR angle. Assuming that differences along the line- of- sight from the different MISR angles are small, the consistency of the TOA fluxes provides an indication of the instantaneous TOA flux uncertainty. The overall relative consistency of all- sky ocean TOA fluxes is 6% ( 17 W m-(2)). When stratified by cloud type, TOA fluxes are consistent to 2 - 3% ( < 10 W m(-2)) for moderately thick overcast clouds, which make up 15% of the total population.