Measuring and modelling photosynthetically active radiation in Tibet Plateau during April–October

• Published in: Agricultural and forest meteorology 2000-05, Vol.102 (2), p.207-212
• Main Authors: Zhang, Xianzhou, Zhang, Yiguang, Zhoub, Yunhua
• Format: Article
• Language: English
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agricultural and forest meteorology; Agronomy. Soil science and plant productions; atmospheric pressure; Biological and medical sciences; Crop climate. Energy and radiation balances; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; light intensity; mathematical models; measurement; PAR; simulation models; Solar radiation; spectral analysis; Tibet Plateau; vapor pressure; water vapor; wavelengths
• ISSN: 0168-1923; 1873-2240
• DOI: 10.1016/S0168-1923(00)00093-9

Based on the measured data of spectral solar radiation in Lhasa, Tibet from 15 April to 15 October 1994, the ratio of photosynthetically active radiation (PAR) to solar global radiation was presented, i.e. η PAR=0.439±0.014, and 1 J energy of PAR is equivalent to 4.43 μmol quantum. In the climatological estimation of Tibet Plateau, following equations can be used to estimate the daily total PAR energy flux density Q PAR (MJ m −2 per day) and daily total PAR photo flux density U PAR(mol photon m −2 per day): Q PAR =(0.3914+0.0190 ln E ∗) Q U PAR =(1.7339+0.0842 ln E ∗) Q Here, Q (MJ m −2 per day) is the daily global radiation. E*= E P 0/ P, E (hpa) is the water vapor pressure at site, P 0(hpa) is the standard atmosphere pressure at sea level, P (hpa) is the atmosphere pressure at site.