Method for Calculating Photosynthetically Active Radiation in Xinglong Region
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Abstract:
Integrated observations were made of the solar radiation, including photosynthetically active radiation (PAR), visible radiation (VIS), global radiation (Q), etc, and meteorological parameters at Xinglong, Hebei Province, from 11 September 2005 to 2 September 2006. The variation characteristics of PAR and VIS were obtained. The results show that the ratios of hourly sum of PAR to Q, VIS to Q, and PAR to VIS are relatively stable, and their averages are 2.03 (mol/MJ), 0.42 and 4.89 (mol/MJ), respectively,which indicate the obvious diurnal, daily and seasonal variations, being influenced by water vapor, aerosol, clouds, etc. The empirical formulas under all sky conditions for calculating the hourly sums of PAR and VIS, and the conversion relationship between hourly sums of PAR and VIS are built. The calculated PAR and VIS are in good agreement with the measured, and their relative biases are 13.3% and 12.1%, respectively, when the water vapor and scattering factor are considered. Concerning the actual condition, when only water vapor factor was considered, their relative biases are 13.8% and 12.4%, respectively. In view of the transmission and calculation of PAR and VIS, the water vapor factor plays an important role, and the role of aerosol is not as important as water vapor, but it should still be considered.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.