The climatological characteristics of clearness indices of global solar radiation (KT) was analysed in terms of its temporal and spatial variation. Comparison between the global solar radiation (G) and the erythemal ultraviolet radiation (EUV) were also performed based on not only the monthly mean values of the irradiance but also their atmospheric transmittances by using ground based measurements in Korean peninsula. The KT showed high values in autumn (KT=0.51 in October) and spring (KT=0.49 in March), and low value in summer (KT=0.37 in July) when the Korean peninsula is affected by North Pacific High. Meanwhile monthly mean values of G and EUV exhibited quite different annual pattern that implying the atmospheric attenuating factors such as clouds, water vapors, aerosols, and ozone have different extinction effects on two radiation. This study suggested that the clouds have larger attenuation effect on G then on EUV while aerosols have larger influence on EUV.
According to methodologies suggested in previous studies, two empirical models for estimating EUV are developed by using ground based radiation data and total ozone measured in OMI and OMPS in four sites in Korea. The two models (model 1 and model 2) showed good performance but commonly displayed underestimation especially in the high EUV. In this regard, this study revised models by classifying whole data according to the KT value and presented improved results in terms of statistical estimators such as R2, RMSE, MAE, MAPE, MAE and slope value. The improved models (model 1'' and model 2'') appeared good performances in temporal validation showing high mean R2 values of 0.90 and 0.89 for two models, respectively. Furthermore spatial validation of the models'' have confirmed possibility of model expansion for the entire Korean peninsula. It is expected that these empirical models presented in this study are useful for analyzing long-term trend and climatological characteristics of the EUV over the Korea.