CERES Aqua Edition2A SSF Data Quality Summary TOA Fluxes - Accuracy and Validation

CERES shortwave (SW), longwave (LW), and window (WN) channel radiative fluxes are derived from empirical Angular Distribution Models (ADMs) that convert a measured radiance in a given Sun-Earth-satellite viewing configuration to a top-of-atmosphere (TOA) radiative flux. The first set of CERES ADMs were developed from 9 months of CERES TRMM SSF measurements over the Tropics (Loeb et al., 2003a,b). These ADMs were used to generate TOA fluxes on the CERES TRMM Edition2B SSF product. The TRMM ADMs were also used to produce TOA fluxes for the CERES Terra Edition1A SSF product while a new set of global ADMs based on CERES Terra data were being developed. Once the new global CERES Terra ADMs were completed (Loeb et al., 2004), these were used to generate TOA fluxes on the CERES Terra Edition2B SSF product. Loeb et al. (2006) provide a detailed assessment of the uncertainties in CERES Terra Edition2B SSF fluxes.

The CERES Aqua Edition1B SSF data product used the CERES Terra ADMs while a new set of ADMs based on CERES Aqua data were being developed. The methodology used to develop the new Aqua ADMs is based on the same approach as that used to develop Terra ADMs (Loeb et al., 2004). The new Aqua ADMs are now complete and are being used to generate TOA fluxes on the CERES Aqua Edition2A SSF product. The new Aqua ADMs are based on 24 months (August 2002 - June 2004). The main features of the new Aqua ADMs are given below. For a more detailed description of the CERES Terra ADMs see Loeb et al. (2004).

• Empirical ADMs over snow and sea-ice.
• Increased angular resolution in nonpolar regions (2 degrees)
• Use of "continuous" SW and LW ADM scene types over ocean, land, and desert.
• Monthly 1 degree regional clear land+desert ADMs.
• Neural network scheme to improve TOA flux estimates for footprints with excessive "no retrievals". No retrievals can occur when imager data is missing or when the cloud algorithm cannot provide a physical retrieval. If the scene characteristics over 35% or more of a CERES FOV are unknown, TOA fluxes are estimated using a neural network scheme. Approximately 3% of the CERES data fall in this category.

While CERES Terra and CERES Aqua TOA flux errors are generally quite similar (Loeb et al., 2006), differences are observed in polar regions. Biases in daytime SW TOA fluxes from Aqua ADMs are significantly smaller than Terra fluxes over sea-ice. In contrast, when the new Aqua ADMs were first applied to infer LW TOA fluxes over the Antarctic Plateau, Aqua TOA flux errors were found to be significantly larger than those from Terra ADMs. The cause for these discrepancies is associated with differences between the Terra and Aqua CERES polar cloud mask applied to MODIS. To avoid the biases in Aqua LW TOA fluxes over the nighttime Antarctic Plateau, we've replaced the original Aqua nighttime LW permanent snow ADMs with those developed on Terra in Ed2A processing. A more detailed discussion of the differences is provided in Loeb et al. (2006).

The tables below provide additional details on Aqua ADM scene classification and validation results. Further details can be found in the following:

• http://science.larc.nasa.gov/ceres/STM/2005-11/loeb_adm.pdf (PDF)
• Loeb et al. (2006) paper (PDF)

Instantaneous TOA Flux Consistency (nadir vs θ=50-60 deg)

Regional TOA Flux Uncertainties

Comparison Between Edition1B and Edition2A Aqua TOA Fluxes

CERES Aqua Edition2A mean all-sky SW TOA flux (top), CERES Aqua Edition1B minus Edition2A mean all-sky SW TOA flux difference (middle) and RMS difference (bottom) for January 2003.

CERES Aqua Edition2A mean all-sky SW TOA flux (top), CERES Aqua Edition1B minus Edition2A mean all-sky SW TOA flux difference (middle) and RMS difference (bottom) for July 2003.

CERES Aqua Edition2A mean all-sky LW TOA flux (top), CERES Aqua Edition1B minus Edition2A mean all-sky LW TOA flux difference (middle) and RMS difference (bottom) for January 2003 (daytime only).

CERES Aqua Edition2A mean all-sky LW TOA flux (top), CERES Aqua Edition1B minus Edition2A mean all-sky LW TOA flux difference (middle) and RMS difference (bottom) for July 2003 (daytime only).