| Basic characteristics of photosynthetically active radiation and its climatological calculation on Changwu tableland |
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| DOI：10.7606/j.issn.1000-7601.2012.04.30 |
| Key Words: Changwu tableland photosynthetically active radiation global radiation climatological calculation |
| Author Name | Affiliation | | HAN Xiaoyang | College of Forestry, Northwest A & F University, Yangling, Shaanxi 712100, China | | LIU Wenzhao | Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Yangling, Shaanxi 712100, China | | ZHU Yuanjun | Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Yangling, Shaanxi 712100, China |
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| Abstract: |
| The diurnal and seasonal variation characteristics of the PAR and the ratio of the PAR to global radiation were studied by using the meteorological data from the Changwu Eco-agricultural Experimental Station i
n 2010. The results indicate that the diurnal variations of the PAR and global radiation on typical days have the same trend. The curve for sunny day shows a smooth unimodal feature, while the curve for cloudy day is not stable. The maximum values on both curves appear between 12∶30～15∶00. The PAR is characterized by the obvious seasonal variation and the mean total diurnal quantities of the PAR for the seasons are 6.32, 7.23, 5.63 MJ／(m2·d), and 3.58 MJ／(m2·d) respectively, indicating that the total diurnal quantity is the maximum in spring and summer, the middle in autumn, and the minimum in winter. The ratio of PAR to global radiation in cloudy days is greater than that in sunny days. A maximum value of 0.423 is observed in June, and a minimum value of 0.327 in January. Accordingly, the calculation model of photosynthetically active radiation for the tableland is proposed. |
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