BGD Biogeosciences Discussions BGD Biogeosciences Discuss. 1810-6285 Göttingen, Germany 10.5194/bgd-6-10625-2009 Fast and accurate irradiance calculations for ecosystem models Mobley C. D. 1 Sundman L. K. 2 Bissett W. P. 3 Cahill B. 4 Sequoia Scientific, Inc., 2700 Richards Road, Suite 107, Bellevue, WA 98005, USA Sundman Consulting, 1453 S. Haleyville Circle, Aurora, CO 80018, USA WeoGeo, 2828 SW Corbett Ave., Suite 135, Portland, OR 97201, USA Institute of Marine and Coastal Science, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901, USA 16 11 2009 6 6 10625 10662 Copyright: © 2009 C. D. Mobley et al. 2009 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://bg.copernicus.org/preprints/6/10625/2009/bgd-6-10625-2009.html The full text article is available as a PDF file from https://bg.copernicus.org/preprints/6/10625/2009/bgd-6-10625-2009.pdf

Coupled physical-biological-optical ocean ecosystem models often use sophisticated treatments of their physical and biological components, while oversimplifying the optical component to the possible detriment of the ecosystem predictions. To bring optical computations up to the standard required by recent ecosystem models, we developed a computationally fast numerical model, named EcoLight, that solves the azimuthally averaged radiative transfer equation to obtain accurate in-water spectral irradiances for use in calculations of photosynthesis and photo-oxidation. To evaluate its computational features, we incorporated EcoLight into an idealized physical-biological model for open-ocean Case 1 waters and compared ten-year simulations for a simple analytical irradiance model vs. EcoLight numerical calculations. After optimization, the EcoLight run times are less than 30% more than for the analytical irradiance model. Moreover, EcoLight is suitable for use in Case 2 and optically shallow waters, for which no analytical irradiance models exist. EcoLight also computes ancillary quantities such as the remote-sensing reflectance, which can be useful for ecosystem validation.

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