Phase: RAMI4PILPS
The Institut d’Astronomie et de Géophysique Georges Lemaître (IAGL) model [de Ridder, 1997] is based on the two-stream approximation which consists of dividing the diffuse radiation into isotropic upwelling and downwelling components.
The main difference with the twostream model of Dickinson [1983] is that instead of adopting the single scattering and semi-infinite canopy approximation, the direct beam upscatter coefficient is calculated explicitly.
The motivation for the development of IAGL was to replace simpler schemes in mesoscale atmospheric models and topographic vorticity-mode mesoscale models.
IAGL enforces energy closure.
Having been developed for 1-D canopies the IAGL model was nevertheless also run on the 3-D test cases of RAMI4PILPS.
Pinty et al. [2004a] and Widlowski et al. [2005b] showed that 1-D canopy representations can match all of the radiative properties of 3-D canopies provided that effective instead of true model parameter values for the vegetation layer are specified.
Since the model was, however, run with true instead of effective parameters one may expect larger deviations of the IAGL model over the 3-D test cases of RAMI4PILPS.
