HR: 0800h
AN: A51A-0737    [Abstracts]
TI: Effects of ozone, cloud and snow surface on surface UV irradiance
AU: * Lee, Y
EM: milogon@yonsei.ac.kr
AF: Global Environment Laboratory, Department of Atmospheric Sciences, Yonsei University, 134 Sinchon-dong, Seodaemoon-gu, Seoul, 120-749 Korea, Republic of
AU: Kim, J
EM: jkim2@yonsei.ac.kr
AF: Global Environment Laboratory, Department of Atmospheric Sciences, Yonsei University, 134 Sinchon-dong, Seodaemoon-gu, Seoul, 120-749 Korea, Republic of
AU: Cho, H
EM: chk@yonsei.ac.kr
AF: Global Environment Laboratory, Department of Atmospheric Sciences, Yonsei University, 134 Sinchon-dong, Seodaemoon-gu, Seoul, 120-749 Korea, Republic of
AU: Lee, B
EM: bylee@kopri.re.kr
AF: Korea Polar Research Institute,KORDI, P.O.Box 29, Ansan, 425-600 Korea, Republic of
AB: Total solar irradiance(TSO), total UV irradiance(TUV) and erythemal UV irradiance(EUV) measured at King Sejong station($62.22\deg$S, $58.78\deg$W) in west Antarctica have been used together with total ozone, cloud amount and snow cover to examine the effects of ozone, cloud and snow surface on these surface solar irradiance over the period of 1998$\sim$2003. The data of three solar components for each scan normalized to the mean Sun-Earth distance(1AU) were grouped by cloud amount, n in oktas(0$<=$n$<$3, 3$<=$n$<$4, 4$<=$n$<$5, 5$<=$n$<$6, 6$<=$n$<$7 and 7$<=$n$<=$8) for the solar zenith angle(SZA) over the range of $45\deg$ to $75\deg$. The radiation amplification factor(RAF) is used to quantify ozone effect on EUV. RAF of EUV decreases from 1.51 to 0.94 under clear skies but increases from 0.94 to 1.85 under cloudy skies as SZA increases. It decreases from 1.51 to 1.01 as cloud amount increases. The effects of cloud amount and snow surface on EUV are estimated as a function of SZA and cloud amount after the normalization of the data to the reference total ozone of 300 DU. In order to analyze the transmission of solar radiation by cloud, regression analyses have been performed for the maximum values of solar irradiance on clear sky conditions(0$<=$n$<$3). On cloudy conditions the maximum and minimum transmission can be regarded as thin and thick cloud covers, respectively. The maximum regression values for the clear sky cases were taken to represent minimum aerosol conditions for the site and thus appropriate as a normalization(reference) factor for the other regressions. In comparison with the three components of the solar irradiance under thin and thick cloud covers, it is found that the transmission is the largest in TUV and the smallest in TSO among the three components of the solar irradiance for the specific SZA. We also noted that the transmission by thin cloud covers is enhanced significantly due to multiple scattering and reflection by the clouds. The relative difference between snow surface and snow-free surface in EUV slowly increases from $9%$ to $20%$ as total ozone increases from 100 DU to 400 DU under partly cloud conditions(3$<=$n$<$6) at SZA $60\deg$. The snow effects on TUV and TSO are relatively high with $32%$ and $34%$, respectively, under clear sky conditions, while the effects changes to $36%$ and $20%$ for TUV and TSO, respectively, as cloud amount increases.
DE: 0360 Transmission and scattering of radiation
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting