Atmospheric Transmission of Ultraviolet and Total Solar Radiation by Clouds, Aerosols, and Ozone in Seoul, Korea: a Comparison of Semi-Empirical Model Predictions with Observations

Abstract

This study examines the semi-empirical models to evaluate the atmospheric broadband transmission of erythemally weighted ultraviolet (EUV), total ultraviolet (TUV), and global solar radiation (GS) by clouds, aerosols, and ozone in Seoul, Korea (37.57°N, 128.98°E). Climatological values of surface solar irradiance (SSI) for Seoul are briefly summarized, and atmospheric transmission is defined as the ratio of measured SSI to clear-sky irradiance calculated using harmonic analysis. Three multiple linear regression models are developed for the EUV, TUV, and GS spectral bands for all-sky (clear and cloudy conditions) transmission using three independent variables: cloud-cover amount, aerosol optical depth, and total ozone. The modeled total transmissions are 75%, 71%, and 67% for the EUV, TUV, and GS spectral bands, respectively, which are slightly overestimated than the measured values. The modeled annual mean clearness index, KT, is 1%, 45%, and 48% for the three spectral bands, respectively. Four semi-empirical models were developed to calculate transmission and were evaluated. Among the various empirical models, estimates from the exponential models were found to be the closest to measured values, having the lowest mean bias error (−0.3% to −2.4%) and highest explained variance (R2 = 0.17 to 0.50; p = 0.000), as was expected from their theoretical bases. The annual average transmissions of cloud, aerosol, ozone, and all three combined show decrease from the EUV to the TUV and GS bands.