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The fourth phase of the radiative transfer model intercomparison (RAMI) exercise: Actual canopy scenarios and conformity testing

Jean-Luc Widlowski 1 Corrado Mio 1 Mathias Disney 2, 3 Jennifer Adams 1, 2 Ioannis Andredakis 4 Clément Atzberger 5 James Brennan 2, 3 Lorenzo Busetto 6 Michaël Chelle 7 Guido Ceccherini 1 Roberto Colombo 8 Jean-François Côté 9 Alo Eenmäe 10, 11 Richard Essery 12 Jean-Philippe Gastellu-Etchegorry 13 Nadine Gobron 1 Eloi Grau 13 Vanessa Haverd 14 Lucie Homolova 15 Huaguo Huang 16 Linda Hunt 17 Hideki Kobayashi 18 Benjamin Koetz 19 Andres Kuusk 11 Joel Kuusk 11 Mait Lang 10, 11 Philip E. Lewis 2, 3 Jennifer L. Lovell 20 Zbynek Malenovsky 21 Michele Meroni 4 Felix Morsdorf 22 Matti Mottus 23 Wenge Ni-Meister 24 Bernard Pinty 4 Miina Rautiainen 25 Martin Schlerf 26 Ben Somers 27 Jan Stuckens 28 Michel M. Verstraete 29, 30 Wenze Yang 31 Feng Zhao 32 Terenzio Zenone 33
Abstract : The RAdiative transfer Model Intercomparison (RAMI) activity focuses on the benchmarking of canopy radiative transfer (RT) models. For the current fourth phase of RAMI, six highly realistic virtual plant environments were constructed on the basis of intensive field data collected from (both deciduous and coniferous) forest stands as well as test sites in Europe and South Africa. Twelve RT modelling groups provided simulations of canopy scale (directional and hemispherically integrated) radiative quantities, as well as a series of binary hemispherical photographs acquired from different locations within the virtual canopies. The simulation results showed much greater variance than those recently analysed for the abstract canopy scenarios of RAMI-IV. Canopy complexity is among the most likely drivers behind operator induced errors that gave rise to the discrepancies. Conformity testing was introduced to separate the simulation results into acceptable and non-acceptable contributions. More specifically, a shared risk approach is used to evaluate the compliance of RT model simulations on the basis of reference data generated with the weighted ensemble averaging technique from ISO-13528. However, using concepts from legal metrology, the uncertainty of this reference solution will be shown to prevent a confident assessment of model performance with respect to the selected tolerance intervals. As an alternative, guarded risk decision rules will be presented to account explicitly for the uncertainty associated with the reference and candidate methods. Both guarded acceptance and guarded rejection approaches are used to make confident statements about the acceptance and/or rejection of RT model simulations with respect to the predefined tolerance intervals.
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Jean-Luc Widlowski, Corrado Mio, Mathias Disney, Jennifer Adams, Ioannis Andredakis, et al.. The fourth phase of the radiative transfer model intercomparison (RAMI) exercise: Actual canopy scenarios and conformity testing. Remote Sensing of Environment, Elsevier, 2015, 169, pp.418-437. ⟨10.1016/j.rse.2015.08.016⟩. ⟨hal-02638630⟩



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