Estimating the photosynthetically active radiation under clear skies by means of a new approach

Nyamsi, William Wandji; Espinar, Bella; Blanc, Philippe; Wald, Lucien

doi:10.5194/asr-12-5-2015

Cited by 17 publications

(16 citation statements)

References 9 publications

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“…When the PAR estimates from the technique were compared against the values obtained by the detailed spectral calculations of libRadtran, Wandji Nyamsi et al [30] found no systematic bias as a function of any inputs. In addition, there was no systematic bias or trend as a function of the PAR intensity.…”

Section: Discussionmentioning

confidence: 99%

“…The resampling technique has been presented in Wandji Nyamsi et al [30,37] for the PAR range and UV range, respectively. The technique is a pure modelling concept with radiative transfer simulations with libRadtran.…”

Section: Description Of the Spectral Resampling And The Proposed Methodsmentioning

confidence: 99%

“…First, a set of 60,000 atmospheric condition parameters in cloudless atmospheres has been built with Monte-Carlo draws, following the statistical distribution of each input, as reported in Table 2 in Wandji Nyamsi et al [30]. For each condition, libRadtran is run twice for both the direct and global irradiances: one with the Kato et al [26] scheme and the other with the detailed spectral calculations every 1 nm.…”

Section: Description Of the Spectral Resampling And The Proposed Methodsmentioning

confidence: 99%

“…A numerical validation of the new method was performed in Wandji Nyamsi et al [30] by comparing the results to the PAR fluxes given by the detailed spectral calculations in libRadtran. Both the relative bias in the absolute value and the root mean square error reached a maximum of 1% for both the direct and global PAR fluxes.…”

Section: Description Of the Spectral Resampling And The Proposed Methodsmentioning

confidence: 99%

“…The eleven KBs covering the PAR spectral interval are KB #6 [0.363, 0.408] µm to KB #16 [0.684, 0.704] µm. Wandji Nyamsi et al [30] have reported on a resampling technique over the PAR range that gives the irradiance for every 1 nm within each KB over the PAR range from the irradiance of 30 nm width of each KB in any atmospheric state in cloudless conditions. The technique is explained in more detail in Section 3.2.…”

Section: Introductionmentioning

confidence: 99%

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A New Clear-Sky Method for Assessing Photosynthetically Active Radiation at the Surface Level

et al. 2019

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A clear-sky method to estimate the photosynthetically active radiation (PAR) at the surface level in cloudless atmospheres is presented and validated. It uses a fast and accurate approximation adopted in several radiative transfer models, known as the k-distribution method and the correlated-k approximation, which gives a set of fluxes accumulated over 32 established wavelength intervals. A resampling technique, followed by a summation, are applied over the wavelength range [0.4, 0.7] µm in order to retrieve the PAR fluxes. The method uses as inputs the total column contents of ozone and water vapor, and optical properties of aerosols provided by the Copernicus Atmosphere Monitoring Service. To validate the method, its outcomes were compared to instantaneous global photosynthetic photon flux density (PPFD) measurements acquired at seven experimental sites of the Surface Radiation Budget Network (SURFRAD) located in various climates in the USA. The bias lies in the interval [−12, 61] µmol m −2 s −1 ([−1, 5] % in values relative to the means of the measurements at each station). The root mean square error ranges between 37 µmol m −2 s −1 (3%) and 82 µmol m −2 s −1 (6%). The squared correlation coefficient fluctuates from 0.97 to 0.99. This comparison demonstrates the high level of accuracy of the presented method, which offers an accurate estimate of PAR fluxes in cloudless atmospheres at high spatial and temporal resolutions useful for several bio geophysical models.

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Section: Discussionmentioning

confidence: 99%

Section: Description Of the Spectral Resampling And The Proposed Methodsmentioning

confidence: 99%

Section: Description Of the Spectral Resampling And The Proposed Methodsmentioning

confidence: 99%

Section: Description Of the Spectral Resampling And The Proposed Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A New Clear-Sky Method for Assessing Photosynthetically Active Radiation at the Surface Level

et al. 2019

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Detecting clear‐sky periods from photovoltaic power measurements

Wandji Nyamsi,

Lindfors

2024

Meteorological Applications

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A method for detecting clear‐sky periods from photovoltaic (PV) power measurements is presented and validated. It uses five tests dealing with parameters characterizing the connections between the measured PV power and the corresponding clear‐sky power. To estimate clear‐sky PV power, a PV model has been designed using as inputs downwelling shortwave irradiance and its direct and diffuse components received at ground level under clear‐sky conditions as well as reflectivity of the Earth's surface and extraterrestrial irradiance, altogether provided by the McClear service. In addition to McClear products, the PV model requires wind speed and temperature as inputs taken from ECMWF twentieth century reanalysis ERA5 products. The performance of the proposed method has been assessed and validated by visual inspection and compared to two well‐known algorithms identifying clear‐sky periods with broadband global and diffuse irradiance measurements on a horizontal surface. The assessment was carried out at two stations located in Finland offering collocated 1‐min PV power and broadband irradiance measurements. Overall, total agreement ranges between 84% and 97% (depending on the season) in discriminating clear‐sky and cloudy periods with respect to the two well‐known algorithms serving as reference. The disagreement fluctuating between 6% and 15%, depending on the season, primarily occurs while the PV module temperature is adequately high and/or when the sun is close to the horizon with many more interactions between the radiation, the atmosphere and the ground surface.

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Gesture Recognition in 3D Space Using Dimensionally Reduced Set of Features

Gadomer

Skoczylas

2017

Computer Information Systems and Industrial Management

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Part 3: Data Analysis and Information RetrievalInternational audienceIn this study authors present a solution to track and recognize arbitrary gestures of hands in three dimensional space and review the recognition accuracy. The idea of this novel gesture recognition system is described and results of research made on a recorded gesture data set are presented. Gesture instances were defined by user standing in different distances from the controller, in different placements of their field of vision and with different speeds, making recognition velocity and position invariant. Authors’ goal was to find the minimal number of features that give satisfying gesture classification result in order to achieve a compromise between accuracy and computation time. In this publication progress of the research on gesture recognition problem is described and a comparative study is presented

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Estimating the photosynthetically active radiation under clear skies by means of a new approach

Cited by 17 publications

References 9 publications

A New Clear-Sky Method for Assessing Photosynthetically Active Radiation at the Surface Level

A New Clear-Sky Method for Assessing Photosynthetically Active Radiation at the Surface Level

Detecting clear‐sky periods from photovoltaic power measurements

Gesture Recognition in 3D Space Using Dimensionally Reduced Set of Features

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