ICRCCM - III Description

The Intercomparison of Radiation Codes in Climate Models program (ICRCCM) [Ellingson and Fouquart, 1991] was initiated by the Joint Scientific Committee of the World Climate Research Program (WCRP) and the International Radiation Commission (IRC) of the International Association of Meteorology and Atmospheric Physics (IAMAP) with the goal of evaluating and improving solar and longwave calculations used in climate models.  The initial phase of this effort produced a thorough evaluation of the performance of such models in the solar [Fouquart et al., 1991] and longwave [Ellingson et al., 1991] regimes as of the early 1990's.

The objectives of the current phase of this program, ICRCCM - III [Barker et al., 2002], are:
1) to assess the perfomance of modern 1D solar radiative transfer codes, documenting whether the accuracy of these models has improved compared with the results of the Fouquart et al. [1991] study
2) to evaluate how well 1D solar radiative transfer codes compute broadband irradiances and heating rates when they operate on partially cloudy atmospheres generated by cloud-resolving models.

The participants in this study ran their models for a variety of atmospheric cases.  Benchmark calculations were performed for clear-sky and homogeneously cloudy cases using CHARTS (Code for High-Resolution Accelerated Radiative Transfer [Moncet and Clough, 1997] and for cases with unresolved clouds using four 3D Monte Carlo algorithms, which had been validated for the clear-sky and homogeneous cloud cases as producing results comparable to the CHARTS benchmark calculations.

Atmospheric and Environmental Research