Estimating the photosynthetically active radiation under clear skies by means of a new approach
The <i>k</i>-distribution method and the correlated-<i>k</i> approximation of Kato et al. (1999) is a computationally efficient approach originally designed for calculations of the broadband solar radiation by dividing the solar spectrum in 32 specific spectral bands from 240...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2015-02-01
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| Series: | Advances in Science and Research |
| Online Access: | http://www.adv-sci-res.net/12/5/2015/asr-12-5-2015.pdf |
| _version_ | 1818367502823981056 |
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| author | W. Wandji Nyamsi B. Espinar P. Blanc L. Wald |
| author_facet | W. Wandji Nyamsi B. Espinar P. Blanc L. Wald |
| author_sort | W. Wandji Nyamsi |
| collection | DOAJ |
| description | The <i>k</i>-distribution method and the correlated-<i>k</i> approximation of Kato et al. (1999)
is a computationally efficient approach originally designed for
calculations of the broadband solar radiation by dividing the solar spectrum
in 32 specific spectral bands from 240 to 4606 nm. This paper describes a
technique for an accurate assessment of the photosynthetically active
radiation (PAR) from 400 to 700 nm at ground level, under clear-sky
conditions using twelve of these spectral bands. It is validated against
detailed spectral calculations of the PAR made by the radiative transfer
model libRadtran. For the direct and global PAR irradiance, the bias is
−0.4 W m<sup>−2</sup> (−0.2%) and −4 W m<sup>−2</sup> (−1.3%)
and the root mean square error is 1.8 W m<sup>−2</sup> (0.7%) and
4.5 W m<sup>−2</sup> (1.5%). For the direct and global Photosynthetic Photon
Flux Density, the biases are of about +10.3 μmol m<sup>−2</sup> s<sup>−1</sup> (+0.8%)
and 1.9 μmol m<sup>−2</sup> s<sup>−1</sup> (−0.1%) respectively, and the root mean
square error is 11.4 μmol m<sup>−2</sup> s<sup>−1</sup> (0.9%) and
4.0 μmol m<sup>−2</sup> s<sup>−1</sup> (0.3%). The correlation
coefficient is greater than 0.99. This technique provides much better
results than two state-of-the-art empirical methods computing the daily mean
of PAR from the daily mean of broadband irradiance. |
| first_indexed | 2024-12-13T22:53:05Z |
| format | Article |
| id | doaj.art-21547c6d417f4dccac06b93ec705c0da |
| institution | Directory Open Access Journal |
| issn | 1992-0628 1992-0636 |
| language | English |
| last_indexed | 2024-12-13T22:53:05Z |
| publishDate | 2015-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Advances in Science and Research |
| spelling | doaj.art-21547c6d417f4dccac06b93ec705c0da2022-12-21T23:28:34ZengCopernicus PublicationsAdvances in Science and Research1992-06281992-06362015-02-011251010.5194/asr-12-5-2015Estimating the photosynthetically active radiation under clear skies by means of a new approachW. Wandji Nyamsi0B. Espinar1P. Blanc2L. Wald3MINES ParisTech, PSL Research University, O. I. E. – Centre Observation, Impacts, Energy, Sophia Antipolis CEDEX, FranceMINES ParisTech, PSL Research University, O. I. E. – Centre Observation, Impacts, Energy, Sophia Antipolis CEDEX, FranceMINES ParisTech, PSL Research University, O. I. E. – Centre Observation, Impacts, Energy, Sophia Antipolis CEDEX, FranceMINES ParisTech, PSL Research University, O. I. E. – Centre Observation, Impacts, Energy, Sophia Antipolis CEDEX, FranceThe <i>k</i>-distribution method and the correlated-<i>k</i> approximation of Kato et al. (1999) is a computationally efficient approach originally designed for calculations of the broadband solar radiation by dividing the solar spectrum in 32 specific spectral bands from 240 to 4606 nm. This paper describes a technique for an accurate assessment of the photosynthetically active radiation (PAR) from 400 to 700 nm at ground level, under clear-sky conditions using twelve of these spectral bands. It is validated against detailed spectral calculations of the PAR made by the radiative transfer model libRadtran. For the direct and global PAR irradiance, the bias is −0.4 W m<sup>−2</sup> (−0.2%) and −4 W m<sup>−2</sup> (−1.3%) and the root mean square error is 1.8 W m<sup>−2</sup> (0.7%) and 4.5 W m<sup>−2</sup> (1.5%). For the direct and global Photosynthetic Photon Flux Density, the biases are of about +10.3 μmol m<sup>−2</sup> s<sup>−1</sup> (+0.8%) and 1.9 μmol m<sup>−2</sup> s<sup>−1</sup> (−0.1%) respectively, and the root mean square error is 11.4 μmol m<sup>−2</sup> s<sup>−1</sup> (0.9%) and 4.0 μmol m<sup>−2</sup> s<sup>−1</sup> (0.3%). The correlation coefficient is greater than 0.99. This technique provides much better results than two state-of-the-art empirical methods computing the daily mean of PAR from the daily mean of broadband irradiance.http://www.adv-sci-res.net/12/5/2015/asr-12-5-2015.pdf |
| spellingShingle | W. Wandji Nyamsi B. Espinar P. Blanc L. Wald Estimating the photosynthetically active radiation under clear skies by means of a new approach Advances in Science and Research |
| title | Estimating the photosynthetically active radiation under clear skies by means of a new approach |
| title_full | Estimating the photosynthetically active radiation under clear skies by means of a new approach |
| title_fullStr | Estimating the photosynthetically active radiation under clear skies by means of a new approach |
| title_full_unstemmed | Estimating the photosynthetically active radiation under clear skies by means of a new approach |
| title_short | Estimating the photosynthetically active radiation under clear skies by means of a new approach |
| title_sort | estimating the photosynthetically active radiation under clear skies by means of a new approach |
| url | http://www.adv-sci-res.net/12/5/2015/asr-12-5-2015.pdf |
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