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Open AccessArticle

Estimating Cloud and Aerosol UV Modification Factors Based on Spectral Measurement from the Brewer Spectrophotometer

School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, Korea
Department of Atmospheric Sciences, Chungnam National University, Daejeon 34134, Korea
Division of Earth and Environmental System Science Major of Spatial Information Engineering, Pukyong National University, Busan 48513, Korea
Department of Atmospheric Sciences, Yonsei University, Seoul 03722, Korea
Author to whom correspondence should be addressed.
Atmosphere 2017, 8(6), 109;
Received: 10 May 2017 / Revised: 14 June 2017 / Accepted: 15 June 2017 / Published: 19 June 2017
(This article belongs to the Section Aerosols)
Cloud and aerosol modification factors are investigated in the spectral range of ultraviolet (UV) to correct for cloud and aerosol extinction effects from clear sky irradiance. The cloud modification factor (CMF) and aerosol modification factor (AMF) are estimated using radiative transfer model (RTM) simulations and ground-based observations in Seoul, Korea. The modification factors show a spectral dependence within the spectral range of 300 to 360 nm, which is the range used to estimate erythemal UV. The CMF and AMF values are estimated with high spectral resolution with considerations of solar zenith angle (SZA), cloud/aerosol amount, and total ozone variation. From the simulation studies, the variation in the CMFs within the spectral range of 300–360 nm is estimated to be 0.031–0.055, which is twice as large as the decrease in CMFs resulting from a SZA increase of 10°. In addition, the CMFs estimated from observational data show significant spectral dependence, varying from 2.5% to 10.0%. Because of the small aerosol optical depth (AOD) value, however, the variation in the AMF calculated from simulations is estimated to be between 0.007 and 0.045, indicating lower spectral dependence than the CMF. Furthermore, the spectral difference in the AMF calculated from observational data is insignificant relative to the daily-averaged total ozone error and uncertainties related to the reference irradiance spectrum under aerosol-free conditions. View Full-Text
Keywords: modification factor; cloud; aerosol; erythemal UV modification factor; cloud; aerosol; erythemal UV
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Park, S.S.; Kim, M.; Lee, H.; Lee, H.; Kim, S.-M.; Lee, Y.G. Estimating Cloud and Aerosol UV Modification Factors Based on Spectral Measurement from the Brewer Spectrophotometer. Atmosphere 2017, 8, 109.

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