Radiation Transfer Model Intercomparison (RAMI) exercise: Results from the second phase

Abstract

[1] The Radiation Transfer Model Intercomparison (RAMI) initiative is a communitydriven exercise to benchmark the models of radiation transfer (RT) used to represent the reflectance of terrestrial surfaces. Systematic model intercomparisons started in 1999 as a self-organized, open-access, voluntary activity of the RT modeling community. The results of the first phase were published by Pinty et al. [2001]. The present paper describes the benchmarking protocol and the results achieved during the second phase, which took place during 2002. This second phase included two major components: The first one included a rerun of all direct-mode tests proposed during the first phase, to accommodate the evaluation of models that have been upgraded since, and the participation of new models into the entire exercise. The second component was designed to probe the performance of three-dimensional models in complex heterogeneous environments, which closely mimic the observations of actual space instruments operating at various spatial resolutions over forest canopy systems. Phases 1 and 2 of RAMI both confirm not only that a majority of the radiation transfer models participating in RAMI are in good agreement between themselves for relatively simple radiation transfer problems but also that these models exhibit significant discrepancies when considering more complex but nevertheless realistic geophysical scenarios. Specific recommendations are provided to guide the future of this benchmarking program (Phase 3 and beyond).

Discrete Anisotropic Radiative Transfer (DART 5) for Modeling Airborne and Satellite Spectroradiometer and LIDAR Acquisitions of Natural and Urban Landscapes

“…and instrument specifications (spatial and spectral resolutions, sensor viewing directions, platform altitude, etc.). DART forward simulations of vegetation reflectance were successfully verified by real measurements [32] and also cross-compared against a number of independently designed 3D reflectance models (e.g., FLIGHT [26], Sprint [33], Raytran [27]) in the context of the RAdiation transfer Model Intercomparison (RAMI) experiment [34][35][36][37][38]. To date, DART has been successfully employed in various scientific applications, including development of inversion techniques for airborne and satellite reflectance images [39,40], design of satellite sensors (e.g., NASA DESDynl, CNES Pleiades, CNES LIDAR mission project [41]), impact studies of canopy structure on satellite image texture [42] and reflectance [32], modeling of 3D distribution of photosynthesis and primary production rates in vegetation canopies [43], investigation of influence of Norway spruce forest structure and woody elements on canopy reflectance [44], design of a new chlorophyll estimating vegetation index for a conifer forest canopy [45], and studies of tropical forest texture [46][47][48], among others.…”

Investigating the Utility of Wavelet Transforms for Inverting a 3-D Radiative Transfer Model Using Hyperspectral Data to Retrieve Forest LAI

“…The model output predicts any specified directional sensor response. It was compared and tested within the European Commission Radiation Transfer Model Intercomparison (RAMI) experiment [21] and had an unprecedented level of agreement with other candidate models in simulating heterogeneous canopy spectra [13].…”

Remote Sensing Studies of Urban Canopies: 3D Radiative Transfer Modeling

“…DART forward simulations of vegetation reflectance were successfully verified by real measurements [12] and also cross-compared against a number of independently designed 3D reflectance models (e.g., FLIGHT [13], Sprint [14], Raytran [15]) in the context of the RAdiation transfer Model Intercomparison (RAMI) experiment [16,17].…”