Estimation of Daily Solar Radiation from Sunshine Duration in Thailand
Satoshi WATANABE, Daisuke KOMORI
Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
Masatoshi AOKI
Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan
Wonsik KIM
National Institute for Agro-Environmental Sciences (NIAES), Tsukuba, Japan
Samakkee BOONYAWAT, Piyapong TONGDEENOK
Faculty of Forestry, Kasetsart University, Bongkok, Thailand
Saman PRAKARNRAT, and Somchai BAIMOUNG
Thai Meteorological Department (TMD), Bangkok, Thailand
(Manuscript received 31 May 2010, in final form 3 November, 2010)
Abstract
The empirical relationship between solar radiation and sunshine duration in Thailand is studied in this paper. Although regional long-term regional solar radiation has not yet been measured in Thailand, the data of sunshine duration measurements are available. Hence, measurement of global solar radiation is conducted to find the relationship between daily solar radiation and sunshine duration, which is mostly linear. The distribution of regression coe?cients is examined and the formula that can be applied in Thailand is estimated. The e?ciency of the proposed formula is validated through its prediction. The result shows that the accuracy of the country-wide regression equations can be comparable to that constructed at each station. Moreover, it is found that the proposed equations are more e?ective from May to November than from December to April. The proposed equations are applied to estimate solar radiation in Thailand and the di?erences in their prediction are found in the characteristics of statistical distributions between May–November and December–April.
Corresponding author: Satoshi Watanabe, Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
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6 2011, Meteorological Society of Japan
Journal of the Meteorological Society of Japan, Vol. 89A, pp. 355--364, 2011. 355
DOI:10.2151/jmsj.2011-A25
