Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2017-208
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Model description paper
14 Sep 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).
Fast matrix treatment of 3D radiative transfer in vegetation canopies: SPARTACUS-Vegetation 1.0
Robin J. Hogan1,2, Tristan Quaife2, and Renato Braghiere2 1European Centre for Medium-rangeWeather Forecasts, Reading, UK
2Department of Meteorology, University of Reading, Reading, UK
Abstract. A fast scheme is described to compute the 3D interaction of solar radiation with vegetation. The vegetation canopy is split horizontally into one clear region and one or more vegetated regions, and the two-stream equations are used for each, but with additional terms representing lateral exchange of radiation between regions that are proportional to the area of the interface between them. The resulting coupled set of ordinary differential equations is solved using the matrix-exponential method. The scheme is compared to solar Monte Carlo calculations for idealized scenes from the ‘RAMI4PILPS’ intercomparison project, for open forest canopies and shrublands both with and without snow on the ground. Agreement in reflectance, transmittance and canopy absorptance is excellent in both the visible and near infrared. The technique has potential application to weather and climate modelling.

Citation: Hogan, R. J., Quaife, T., and Braghiere, R.: Fast matrix treatment of 3D radiative transfer in vegetation canopies: SPARTACUS-Vegetation 1.0, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2017-208, in review, 2017.
Robin J. Hogan et al.
Robin J. Hogan et al.
Robin J. Hogan et al.

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Short summary
This paper describes a fast new method for calculating how much sunlight is absorbed and reflected by forests and other types of vegetation, rigorously taking account of the complex 3D structure. Careful evaluation show it to perform well even in difficult scenes with snow on the ground. The method is suitable for use within the computer models used to make weather and climate forecasts, where it has the potential to improve predictions of near-surface temperature and photosynthesis rates.
This paper describes a fast new method for calculating how much sunlight is absorbed and...
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