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UV variability in an arid region of Northwest China from measurements and reconstructions
Author(s) -
Wang Lunche,
Gong Wei,
Feng Lan,
Hu Bo
Publication year - 2014
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.4099
Subject(s) - sky , overcast , environmental science , mean squared error , zenith , atmospheric sciences , climatology , ultraviolet , mean absolute error , meteorology , mathematics , geography , physics , statistics , remote sensing , optics , geology
Ultraviolet radiation ( UV ) observed at Fukang ( FK ), China from 2004 to 2012 was used to investigate UV variability and its relationship with global solar radiation ( G ) under various sky conditions in Northwest China. Clearness index ( K t ) was used for characterizing the sky conditions and UV model development, it was discovered that clear skies were the dominated sky conditions (48.72%), followed by partly cloudy (32.56%) and overcast (18.72%) skies. Daily F UV (fraction of UV to G ) increased from November to June with an annual mean of 4.00% at FK . Meanwhile, an efficient all‐sky UV model under any sky conditions has been proposed by investigating the dependence of hourly UV irradiations on K t and cosine of solar zenith angle μ . The model was assessed through the statistical indices: mean bias error ( MBE ), mean absolute bias error ( MABE ) and root mean square error ( RMSE ) whose values were 1.27 (−0.24), 4.64 (4.56) and 6.26% (6.14%), respectively at hourly (daily) basis. The model has also been tested at three other sites with distinctly different climates in China. Finally, daily UV radiation during 1961–2012 in Northwest China was reconstructed and annual mean daily UV irradiation was about 0.603 MJ m −2 d −1 . UV decreased at 0.62 KJ m −2 d −1 decade −1 during the whole study period and the decreases were sharpest in spring (3.28 KJ m −2 d −1 decade −1 ), however, there was an increasing trend at the rate of 2.16 KJ m −2 d −1 year −1 since 1991.