Impact of Scene Dependence on AVHRR Albedo Models

Abstract

Narrowband observations from NOAA's Advanced Very High Resolution Radiometer (AVHRR) are used operationally by NOAA to estimate the earth's broadband planetary albedo. Since May of 1988; these broadband albedo estimates have been derived using the two-channel (visible and near-infrared), scene-independent regression model of Wydick et al. The occurrence of relatively large regional bias errors using this model has led to a study of scene-dependent models that substantially reduce these errors. Three classes of scene stratification are considered: 1) by surface geography type alone (SFC); and 2) and 3) by surface geography type in combination with cloud amount category (SCN) and normalized difference albedo index (NDAI) using AVHRR channels 1 and 2. These and the Wydick model are applied to independent AVHRR global data of 2 July 1985 (hereafter July) and 9 January 1986 (hereafter January). Using ERBE (Earth Radiation Budget Experiment) data as a reference, errors in reflected flux are computed fo... Abstract Narrowband observations from NOAA's Advanced Very High Resolution Radiometer (AVHRR) are used operationally by NOAA to estimate the earth's broadband planetary albedo. Since May of 1988; these broadband albedo estimates have been derived using the two-channel (visible and near-infrared), scene-independent regression model of Wydick et al. The occurrence of relatively large regional bias errors using this model has led to a study of scene-dependent models that substantially reduce these errors. Three classes of scene stratification are considered: 1) by surface geography type alone (SFC); and 2) and 3) by surface geography type in combination with cloud amount category (SCN) and normalized difference albedo index (NDAI) using AVHRR channels 1 and 2. These and the Wydick model are applied to independent AVHRR global data of 2 July 1985 (hereafter July) and 9 January 1986 (hereafter January). Using ERBE (Earth Radiation Budget Experiment) data as a reference, errors in reflected flux are computed fo...