This is the official site of the radiation transfer model intercomparison (RAMI) initiative. RAMI proposes a mechanism to benchmark models designed to simulate the transfer of radiation at or near the Earth's terrestrial surface, i.e., in plant canopies and over soil surfaces. As an open-access, on-going activity, RAMI operates in successive phases each one aiming at re-assessing the capability, performance and agreement of the latest generation of radiation transfer (RT) models. This in turn, will lead to model enhancements and further developments that benefit the RT modelling community as a whole. For more information on RAMI, please consult the FAQs and our privacy and data-usage policy via this DISCLAIMER link.
The first phase of RAMI (RAMI-1) was launched in 1999. Its prime objective was to document the variability that existed between canopy reflectance models when run under well controlled experimental conditions [Pinty et al.,2001, JGR]. The positive response of the various RAMI-1 participants and the subsequent improvements made to a series of radiative transfer (RT) models promoted the launching of the second phase of RAMI (RAMI-2) in 2002. Here the number of test cases was expanded to focus further on the performance of models dealing with structurally complex 3-D plant environments. The main outcomes of RAMI-2 included (1) an increase in the number of participating models, (2) a better agreement between the model simulations in the case of the structurally simple scenes inherited from RAMI-1, and (3) the need to reduce the sometimes substantial differences between some of the 3-D RT models over complex heterogeneous scenes [Pinty et al., 2004, JGR]. The latter issue was noted as one of the challenges that future intercomparison activities would have to face, since the reliable derivation of some sort of ‘‘surrogate truth’’ data set will not be possible in the absence of any agreement between these RT models. This, in turn, would then imply that except in some simple special cases, the evaluation of RT model simulations cannot proceed beyond their mutual comparison because of the general lack of absolute reference standards. During the third phase of RAMI (RAMI-3) - which was held in 2005 and which saw a further increase in the number of participants and test cases with respect to RAMI-1 and 2 – the self-consistency (e.g., energy conservation) together with the absolute and relative performance of RT models were evaluated in great detail [Widlowski et al., 2007a, JGR]. In fact, it became possible to actually demonstrate, for the first time, a general convergence of the ensemble of submitted RT simulations (with respect to RAMI-2), and to document a better than 1% agreement between six of the participating 3-D Monte Carlo RT models.
Related model intercomparison and quality assurance activities include: