Improved Deep Convective Cloud Characterization Designed to Monitor the VIIRS Reflective Solar Band Stability

The NASA CERES project provides the scientific community regional broadband fluxes designed for long-term climate monitoring. The CERES imager and geostationary calibration group (IGCG) has been tasked to radiometrically scale the MODIS, VIIRS and geostationary imagers to a common calibration reference. To achieve this objective the imager records must be stable over time. Although most current imagers have onboard solar diffusers to provide stable calibrated records over time, the IGCG provides its own assessment of the imager stability. The imager stability is based on deep convective cloud (DCC), Libya-4 desert site and Dome-C multiple invariant targets. DCC are spectrally uniform, near-Lambertian natural diffusers offering high signal-to-noise ratio and stable radiometric response in the VIS-NIR spectrum. These characteristics make DCC an effective Earth invariant target for stability monitoring. The IGCG has made progress to improve the SWIR band stability monitoring algorithm by applying channel specific monthly empirical BRDF as well as applying distinct ocean and land BRDFs. The Hu, several theoretical, and empirical BRDFs will be tested across all reflective solar band channels. By mapping the regional DCC reflectance will allow further BRDF optimization. The DCC identified pixels are collectively analyzed using probability density function statistics. The IGCG has tested multiple PDF statistics to determine the best statistic to transfer the calibration of the VIIRS imager with geostationary imagers. The goal is to evaluate the multiple PDF statistics to improve the stability analysis. If time permits, a DCC BRDF designed for the Aqua drifting orbit based on geostationary imager DCC pixels will be constructed and validated with the MODIS imager radiances during the drift period.