Validation of ERBS Scanner Radiances

Richard N. Green Atmospheric Sciences Division, NASA/Langley Research Center, Hampton, Virginia

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Lee M. Avis Atmospheric Sciences Division, NASA/Langley Research Center, Hampton, Virginia

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Abstract

The earth radiation budget satellite (ERBS) has made broadband scanner measurements of the earth radiance for over 5 years. The redundancy between the shortwave, longwave, and total scanning radiometers and data averages have been used to validate the long-term consistency among the measurements and to establish how measurement drift has affected the archived top-of-the-atmosphere fluxes. The total channel gain at night was found to be unchanged over a 4-yr test period. Relative to the total channel at night, the longwave channel sensitivity decreased by 0.5% over the same 4 years and the shortwave channel was unchanged. The shortwave part of the total channel, however, gradually increased in gain by 1.3%. Only the daytime longwave flux was affected by these changes. It drifted upward depending on the scene shortwave component. Over 4 years, the clear ocean daytime longwave flux increased by 0.2% and overcast scenes by 2.6%. For all scenes in the Tropics, the daytime longwave flux increased by less than 1% in 4 years. There was no statistical evidence that the daytime shortwave or nighttime longwave fluxes had drifted.

Abstract

The earth radiation budget satellite (ERBS) has made broadband scanner measurements of the earth radiance for over 5 years. The redundancy between the shortwave, longwave, and total scanning radiometers and data averages have been used to validate the long-term consistency among the measurements and to establish how measurement drift has affected the archived top-of-the-atmosphere fluxes. The total channel gain at night was found to be unchanged over a 4-yr test period. Relative to the total channel at night, the longwave channel sensitivity decreased by 0.5% over the same 4 years and the shortwave channel was unchanged. The shortwave part of the total channel, however, gradually increased in gain by 1.3%. Only the daytime longwave flux was affected by these changes. It drifted upward depending on the scene shortwave component. Over 4 years, the clear ocean daytime longwave flux increased by 0.2% and overcast scenes by 2.6%. For all scenes in the Tropics, the daytime longwave flux increased by less than 1% in 4 years. There was no statistical evidence that the daytime shortwave or nighttime longwave fluxes had drifted.

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