Photosynthetically active radiation in Moldova
Variability of the Photosynthetically Active Radiation (PAR) measured at the ground- based solar radiation monitoring station at the Chisinau site from 2004 to 2006 is analyzed. Series of days with observations for clear sky conditions was selected from the original PAR and solar radiation datase...
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
D.Ghitu Institute of Electronic Engineering and Nanotechnologies
2008
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/6f20641f2e3342b98b3253ffca3902da |
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| Sumario: | Variability of the Photosynthetically Active Radiation (PAR) measured at the ground-
based solar radiation monitoring station at the Chisinau site from 2004 to 2006 is analyzed.
Series of days with observations for clear sky conditions was selected from the original PAR
and solar radiation datasets to study relationship between PAR and global, diffuse and direct
solar irradiance, and to evaluate conversion factor for converting PAR values measured with
specific PAR sensor from photosynthetic photon flux to PAR in energy units. This selection is
necessary to neglect the influence of loudiness upon the measured data. There was proposed
a simple power type relationship approximating diurnal variability of PAR and depending on
aerosol optical depth. There was demonstrated strong positive correlation between daily totals of PAR and global solar radiation both for clear sky and all-sky conditions, and respective
linear equations between these parameters are proposed. Monthly mean values of daily ratios
of PAR and global solar radiation for all-sky conditions show distinct seasonal variation with
large values observed during cloudy months specific to fall and winter seasons. It is attributed
to predominant absorption of solar radiation on aerosols, gases and in clouds occurring outside of PAR spectral domain. For very clear days of observations the growth of daily mean
ratio of PAR and solar irradiance was due to increase of aerosol optical depth. There was supposed a simple linear relationship for evaluation of incoming PAR through direct and diffuse
solar radiation by applying specific weighting coefficients. For all-sky and for clear sky conditions weighting coefficients amount to ~0.46 and ~0.59, respectively. Analysis of radiometric data acquired during one of the clearest day in time series of observation gives conversion
factor which amounts to ~4.65. flux to PAR in energy units. This selection is
necessary to neglect the influence of cloudiness upon the measured data. There was proposed
a simple power type relationship approximating diurnal variability of PAR and depending on
aerosol optical depth. There was demonstrated strong positive correlation between daily totals
of PAR and global solar radiation both for clear sky and all-sky conditions, and respective
linear equations between these parameters are proposed. Monthly mean values of daily ratios
of PAR and global solar radiation for all-sky conditions show distinct seasonal variation with
large value to predominant absorption of solar radiation on aerosols, gases and in clouds occurring outside of PAR spectral domain. For very clear days of observations the growth of daily mean
ratio of PAR and solar irradiance was due to increase of aerosol optical depth. There was supposed a simple linear relationship for evaluation of incoming PAR through direct and diffuse
solar radiation by applying specific weighting coefficients. For all-sky and for clear sky conditions weighting coefficients amount to ~0.46 and ~0.59, respectively. Analysis of radiometric data acquired during one of the clearest day in time series of observation gives conversion factor which amounts to ~4.65. |
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