ORAC Overview

The Optimal Retrieval of Aerosol and Cloud (ORAC) is an optimal estimation scheme that determines aerosol and cloud properties from multispectral imagery ( Thomas et al., 2009,  Thomas et al., 2010,  Sayer et al., 2011,  Poulsen et al., 2012). The scheme uses Discrete Ordinates Radiative Transfer (DISORT,  Stamnes et al., 1988) to model the top of atmosphere radiance as a function of the properties of a plane parallel cloud layer or aerosol with an assumed height distribution. The optimal estimation framework fits the radiance in all channels by varying all retrieved parameters simultaneously, while taking a priori information into account. The scheme also provides error estimates on all retrieved quantities.