Reprocessing NOAA-9 ERBE (Earth Radiation Budget Experiment) Scanner using CERES algorithms and its evaluation with data processed with ERBE algorithms

Earth Radiation Budget Experiment (ERBE) instrument on NOAA-9 measured broadband shortwave and longwave radiance at top-of-atmosphere (TOA) from February 1985 to January 1987. To derive top-of-atmosphere irradiance that is consistent with CERES-derived irradiance, ERBE scanner radiances are reprocessed using more recent CERES algorithms. Cloud properties (fraction, optical thickness, top height, and phase) required for reprocessing are derived using AVHRR data onboard NOAA-9, while no imager data were used in the original ERBE process. The reprocessing increased the NOAA-9 ERBE scanner unfiltered radiances by 1.4%-2.0%, 0.2%-0.3%, and ~1% for daytime and nighttime longwave, shortwave channels, respectively, relative to those derived from ERBE algorithms. In addition, newly derived unfiltered radiances integrated over the field-of-view of the NOAA-9 ERBE nonscanner are compared to assess the calibration. It shows that the NOAA-9 ERBE scanner radiances are larger by 0.9% for shortwave and 0.7% smaller for longwave channel. Moreover, the comparison of irradiances between NOAA-9 and ERBS nonscanner instruments indicates that the NOAA-9 ERBE nonscanner shortwave, nighttime longwave, and daytime longwave irradiances are 0.3% larger, 0.6% smaller, and 0.4% larger, respectively. The CERES algorithms are also used in combination with Ed2 CERES-Aqua ADMs to estimate irradiances from radiance for NOAA-9 ERBE scanner. The global monthly mean of resulting NOAA-9 ERBE scanner irradiances indicates that it is brighter by 1.1% in shortwave, 0.4% warmer in daytime longwave, and 0.8% colder in nighttime longwave, relative to those derived with ERBE algorithms. Comparisons between newly derived ERBE radiances with original radiances produced by the ERBE algorithms, as well as ERBE and CERES derived irradiances will be presented.