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http://dx.doi.org/10.5467/JKESS.2015.36.4.330

Estimation of Total Cloud Amount from Skyviewer Image Data  

Kim, Bu-Yo (Department of Atmospheric & Environmental Sciences, Gangneung-Wonju National University)
Jee, Joon-Bum (Weather Information Service Engine, Hankuk University of Foreign Studies)
Jeong, Myeong-Jae (Department of Atmospheric & Environmental Sciences, Gangneung-Wonju National University)
Zo, Il-Sung (Research Institute for Radiation-Satellite, Gangneung-Wonju National University)
Lee, Kyu-Tae (Department of Atmospheric & Environmental Sciences, Gangneung-Wonju National University)
Publication Information
Journal of the Korean earth science society / v.36, no.4, 2015 , pp. 330-340 More about this Journal
Abstract
For this study, we developed an algorithm to estimate the total amount of clouds using sky image data from the Skyviewer equipped with CCD camera. Total cloud amount is estimated by removing mask areas of RGB (Red Green Blue) images, classifying images according to frequency distribution of GBR (Green Blue Ratio), and extracting cloud pixels from them by deciding RBR (Red Blue Ratio) threshold. Total cloud amount is also estimated by validity checks after removing sunlight area from those classified cloud pixels. In order to verify the accuracy of the algorithm that estimates total cloud amount, the research analyzed Bias, RMSE, and correlation coefficient compared to records of total cloud amount earned by human observation from the Gangwon Regional Meteorological Administration, which is in the closest vicinity of the observation site. The cases are selected four daily data from 0800 LST to 1700 LST for each season. The results of analysis showed that the Bias in total cloud amount estimated by the Skyviewer was an average of -0.8 tenth, and the RMSE was 1.6 tenths, indicating the difference in total cloud amount within 2 tenths. Also, correlation coefficient was very high, marking an average of over 0.91 in all cases, despite the distance between the two observation sites (about 4 km).
Keywords
total cloud amount; sky image; Skyviewer; CCD camera; human observation;
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Times Cited By KSCI : 7  (Citation Analysis)
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