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Verification of ESAS-Light demonstration version - Task 4

Verification against other RT models - WP4100

The libRadtran model has participated in numerous model intercomparisons and model-measurement comparisons. The libRadtran model has always been within the core group of models that have shown excellent agreement. As such libRadtran has been verified against other models for a variety of atmospheric conditions. Another strength of libRadtran is that it contains several radiative transfer equation solvers. This implies that different solvers may easily be compared and strenghts and weaknesses of the solvers detected. See also WP4300 below.

During the development of ESAS-Light model further checking against other RT-models will be undertaken. This will preferably be done within model intercomparison studies. Furthermore, emphasis will be on areas that have not been well covered until now, especially the IR part of the spectrum.

Analytical solutions - WP4200

The radiative transfer equation is not analytically solveable unless several simplifications and approximations are made. The resulting analytical solutions are often applicable to limited cases which are seldom relevant for the complex problems typically adressed by radiative transfer models. Under the development of radiative solvers these are normally checked against other models and/or against analytical solutions. This, for example, applies for the DISORT solver included in libRadtran. A number of analytical solution for a variety of different radiative transfer problems have been provided by Chandrasekhar, 1950 and Thomas and Stamnes, 1999. Where appropriate the various solvers within libRadtran will be checked against the solutions provided by these authors.

Comparison between various methodologies implemented in ESAS-Light toolbox - WP4300

The different solvers of the ESAS-Light toolbox will be compared for at least 20 test cases over ocean and land surface covering a variety of atmospheric and surface conditions, observational geometries and spectral domains. In particular top-of-atmosphere radiances will be compared. The objective of this comparison is to ensure internal consistency of the demonstration version of ESAS-Light toolbox. The following comparisons will be carried out:

  • DISORT vs. polradtran
  • MYSTIC vs. DISORT
  • MYSTIC vs. polradtran
  • twostream vs. DISORT
  • MYSTIC vs. sdisort
 
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