Diurnal Variations of Outgoing Longwave Radiation and Albedo from ERBE Scanner Data

Abstract

The scanning instruments of the Earth Radiation Budget Experiment provide measurements of instantaneous broadband albedo and outgoing longwave radiation (OLR) with a spatial resolution of about 50 km. Data from the Earth Radiation Budget Satellite (ERBS), which is in an orbit that precesses through local time at the rate of one hour every 3 days, can be used to describe the mean, hourly diurnal variations in the distribution of OLR and albedo on this scale. Much of this variation is caused by cloud type and amount changes. Two-dimensional histograms show the co-evolution of OLR and albedo with the diurnal cycle, and the distribution of albedo?OLR pairings associated with the cloud distribution in a particular region and season. The albedo?OLR pairing characterizes a cloud type and determines its net effect on the energy balance at the top of the atmosphere. Diurnal variations in cloud type and amount in many regions are sufficient to cause substantial errors in radiation budget quantities and cloud properties estimated from observations taken from a single sun-synchronous orbit. Errors in estimated net radiation can be as lame as 50 W m?2 for oceanic stratus regions and for land regions during summer.