1. October 2020
   RAMI V
   Launch of the 5th RAMI phase
2. 2009/2015
   RAMI IV
3. 2008/2009
   RAMI4PILPS
4. 2007
   ROMC
   The RAMI On-line Model Checker
5. 2005
   RAMI 3
6. 2002
   RAMI 2
7. 1999
   RAMI 1

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. RAMI-2 faced an increase in the number of participating models. A better agreement between the model simulations for the structurally simple scenes inherited from RAMI-1 was observed, while it was highlighted the need to reduce the differences between some of the 3-D RT models over complex heterogeneous scenes [Pinty et al., 2004, JGR];

During RAMI-3 (2005) a further increase in the number of participants and experiments, the self-consistency (e.g., energy conservation) together with the absolute and relative performance of RT models were evaluated in detail [Widlowski et al., 2007a, JGR]. In fact, it became possible to demonstrate, for the first time, a general convergence of the whole set of submitted RT simulations (with respect to RAMI-2), and to document an agreement between six of the participating 3-D Monte Carlo RT models, below 1%.

RAMI-IV made use of existing ISO-13528:2005 standard to formalize the evaluation of the RT models’ performances. The pre‐screening of data, the identification of reference solutions, and the choice of proficiency statistics were illustrated with simulation results from the RAMI‐IV “abstract canopy” scenarios. After a series of initial consistency checks, this procedure involved (1) the definition of a tolerance criteria suitable for the determination of proficiency in RT model simulations, (2) the definition of a sufficiently precise reference solution against which the candidate models could be compared, and (3) the selection of appropriate evaluation metrics to quantify the performance of the RT models. For surface albedo simulations in the red and NIR, not a single participant was always matching the GCOS accuracy criteria (3%) for all six of the prescribed canopy architecture types (abstract), unless the required success rate is reduced to even 90%. Some RT models submitted simulation results for less than a quarter of the canopy architectures considered in RAMI-IV. This prevented to define statistically significant conclusions about the model performances for some of the experiments. The simulation performed over the six actual realistic canopies of RAMI-IV, showed much greater variance than those analysed for the abstract canopy scenarios.

Whether the differences observed in the RAMI-IV’s model comparison effort were caused by operator errors/choices or were genuine to the RT formulation/implementation, could not be determined. As a matter of facts, in RAMI-IV some of the more deviating models had never participated in previous phases of RAMI.

RAMI-1 to RAMI-IV showed that the repetition of a given set of experiments in successive intercomparison rounds lead to a gradual improvement of most models. Developers gradually identify and remove model weaknesses and software errors and improve the way the RAMI test cases are implemented in the participating models.

1. 19 October 2020
   Fifth RAMI phase
   Launch of firth RAMI phase
2. 30 November 2021
   End of submission period
3. January 2022
   RAMI V results will be available

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