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| DOI：10.13522/j.cnki.ggps.20180412 |
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| Using the Ångström-Prescott Formula to Calculate Solar Radiation from Sunshine Duration in China |
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HUANG Zhongdong, GUO Yifei, ZHANG Yan, LIANG Zhijie, QI Xuebin
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1. Institute of Farmland Irrigation, Chinese Academy of Agricultural Sciences, Xinxiang 453002, China; 2. Key Laboratory of High-efficient and Safe Utilization of Agricultural Water Resources, Chinese Academy of Agricultural Sciences, Xinxiang 453002, China; 3. School of Water Conservancy and Civil Engineering, Northeast Agricultural University, Haerbin 150030, China
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| Abstract: |
| 【Objective】Duration of sunshine is much easier to measure than solar radiation, and their quantitative relationship is thus useful for regions lacking of solar radiation measurements. This paper aims to examine the feasibility of using the ?ngstr?m-Prescott (?-P) formula to estimate solar radiation. 【Method】Sunshine duration and solar radiation measured in 1958 to 2016 across 114 sites in China were used to evaluate the ?-P formula. Spatial distribution of the coefficient a and b in the ?-P formula across the country was studied using geographic information system.【Result】Comparison with measurements revealed that for a specific site, the ?-P formula was reliable, giving rise to a normalized root mean square error (NRMSE) of 0.103 and a normalized mean absolute error (NMAE) of 0.079. The formula was also spatially scalable, with NRMSE and NMAE being 0.103 and 0.078 respectively. Across the country, the coefficient a and b varied in the range of 0.117~0.345 and 0.345~0.703 respectively, with the coefficient a increasing from southeast to northeast while b varying in the opposite direction. The average NRMSE and NMAE of the calculated monthly average daily solar radiation were 0.105 and 0.081, respectively, at provincial scales.【Conclusion】The ?-P formula accurately describes the relationship between monthly-average solar radiation and sunshine duration in China. For region without metrological data, one can use interpolation to fill the gap. To ensure accuracy, the coefficients a and b in the formula should be spatial dependent, taking values estimated at provincial scale. |
| Key words: solar radiation; sunshine duration; Ångström-Prescott formula; spatial interpolation |
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