Plane Parallel Albedo Biases from Satellite Observations. Part II: Parameterizations for Bias Removal

Abstract

Abstract Using the same satellite observations as in Part I of this paper, the authors explore ways to remove the cloud albedo bias (or plane parallel albedo bias), the difference between the plane parallel homogeneous albedo and the average albedo of independent pixels, in regions similar in size to climate model grid boxes. Scaling regional mean optical depths with the reduction factor of R. F. Cahalan et al. provides albedos close to the independent pixel values. Computed albedos approach the independent pixel values within 0.01 for ∼40% of the regions tested and give standard deviations ∼0.02–0.04. Fitting lognormal distributions to the observed optical depth distributions gives albedos within 0.01 of the independent pixel values more than 70% of the time, with standard deviations ∼0.02–0.06. Gamma distributions are less successful than lognormal distributions, giving acceptable results (average bias ∼0.01–0.02, standard deviation ∼0.05–0.08) only when their parameters are estimated from the maximum l...