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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-508
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-508
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 03 Feb 2020

Submitted as: research article | 03 Feb 2020

Review status
A revised version of this preprint is currently under review for the journal BG.

Wide Discrepancies in the Magnitude and Direction of Modelled SIF in Response to Light Conditions

Nicholas C. Parazoo1, Troy Magney1,2, Alex Norton3, Brett Raczka4, Cédric Bacour5, Fabienne Maignan6, Ian Baker7, Yongguang Zhang8, Bo Qiu8, Mingjie Shi9, Natasha MacBean10, Dave R. Bowling4, Sean P. Burns11,12, Peter D. Blanken11, Jochen Stutz9, Katja Grossman13, and Christian Frankenberg1,2 Nicholas C. Parazoo et al.
  • 1Jet Propulsion Laboratory, California Institute of Technology
  • 2California Institute of Technology
  • 3School of Earth Sciences, University of Melbourne
  • 4School of Biological Sciences, University of Utah
  • 5NOVELTIS, 153 rue du Lac, 31670 Labège, France
  • 6Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL
  • 7Colorado State University
  • 8International Institute for Earth System Sciences, Nanjing University, China
  • 9University of California Los Angeles
  • 10Department of Geography, Indiana University
  • 11Department of Geography, University of Colorado
  • 12National Center for Atmospheric Research
  • 13Institute of Environmental Physics, University of Heidelberg

Abstract. Recent successes in passive remote sensing of far-red solar induced chlorophyll fluorescence (SIF) have spurred development and integration of canopy-level fluorescence models in global terrestrial biosphere models (TBMs) for climate and carbon cycle research. The interaction of fluorescence with photochemistry at the leaf- and canopy- scale provides opportunities to diagnose and constrain model simulations of photosynthesis and related processes, through direct comparison to and assimilation of tower, airborne, and satellite data. TBMs describe key processes relating to absorption of sunlight, leaf-level fluorescence emission, scattering and reabsorption throughout the canopy. Here, we analyze simulations from an ensemble of process-based TBM-SIF models (SiB3, SiB4, CLM4.5, CLM5.0, BETHY, ORCHIDEE, BEPS) at a subalpine evergreen needleleaf forest near Niwot Ridge, Colorado. These models are forced with tower observed meteorological data, and analyzed against continuous far-red SIF and gross primary productivity (GPP) partitioned eddy covariance data at diurnal and synoptic scales during the growing season (July–August 2017). Our primary objective is to summarize the site-level state of the art in TBM-SIF modeling over a relatively short time period (summer) when light, structure, and pigments are similar, setting the stage for regional- to global-scale analyses. We find that these models are generally well constrained in simulating photosynthetic yield, but show strongly divergent patterns in the simulation of absorbed photosynthetic active radiation (PAR), absolute GPP and fluorescence, quantum yields, and light response at leaf and canopy scale. This study highlights the need for mechanistic modeling of non-photochemical quenching in stressed and unstressed environments, and improved representation of light absorption (APAR), distribution of sunlit and shaded light, and radiative transfer from leaf to canopy scale.

Nicholas C. Parazoo et al.

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Status: final response (author comments only)
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Nicholas C. Parazoo et al.

Nicholas C. Parazoo et al.

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Latest update: 03 Jun 2020
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Short summary
Satellite measurements of solar induced chlorophyll fluorescence (SIF) provide a global measure of photosynthetic change. This enables scientists to better track carbon cycle responses to environmental change, and tune biochemical processes in vegetation models for improved simulation of future change. We use tower instrumented SIF measurements and controlled model experiments to assess the state of the art in terrestrial biosphere SIF modeling, and find a wide range of sensitivities to light.
Satellite measurements of solar induced chlorophyll fluorescence (SIF) provide a global measure...
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