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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/bg-2017-512
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2017-512
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 02 Jan 2018

Submitted as: research article | 02 Jan 2018

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

Deriving Photosynthetically Active Radiation at ground level in cloud-free conditions from Copernicus Atmospheric Monitoring Service (CAMS) products

William Wandji Nyamsi1, Phillipe Blanc2, John A. Augustine3, Antti Arola1, and Lucien Wald2 William Wandji Nyamsi et al.
  • 1Finnish Meteorological Institute, Kuopio, Finland
  • 2MINES ParisTech, PSL Research University, Centre Observation, Impacts, Energy, Sophia Antipolis, France
  • 3NOAA Earth System Research Laboratory, Global Monitoring Division (GMD), Boulder, CO 80305, USA

Abstract. A method is described that estimates the photosynthetically active radiation (PAR) at ground level in cloud-free conditions. It uses a fast approximation of the libRadtran radiative transfer numerical model, known as the k-distribution method and the correlated-k approximation of Kato et al. (1999). LibRadtran provides irradiances aggregated over several fixed spectral bands and a spectral resampling is proposed followed by an aggregation in the range [400, 700] nm. The Copernicus Atmosphere Monitoring Service (CAMS) produces daily estimates of the aerosol properties, and total column contents in water vapor and ozone that are input to the method. A comparison of the results is performed against instantaneous measurements of global Photosynthetic Photon Flux Density (PPFD) on a horizontal plane made in cloud-free conditions at seven sites of the Surface Radiation network (SURFRAD) in the USA in various climates. The bias ranges between −12 µmol m−2 s−1 (−1 % of the mean value at Desert Rock) and +61 µmol m−2 s−1 (+5 % at Penn. State Univ). The root mean square error ranges from 37 µmol m−2 s−1 (3 %) to 82 µmol m−2 s−1 (6 %). The coefficient of determination R2 ranges between 0.97 and 0.99. This work demonstrates the quality of the proposed method combined with the CAMS products.

William Wandji Nyamsi et al.

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Interactive discussion

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Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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William Wandji Nyamsi et al.

William Wandji Nyamsi et al.

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Short summary
This paper proposes a new, fast and accurate method for estimating photosynthetically active radiation at ground level in cloud-free conditions at any place and time. The method performs very well with the Copernicus Atmosphere Monitoring Service products as inputs describing the state of the atmosphere. An accuracy that is close to the uncertainty of the measurements themselves is reached. We believe that our research will be widely used in the near future.
This paper proposes a new, fast and accurate method for estimating photosynthetically active...
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