Evolution of erythemal solar radiation in Córdoba, Argentina: Effects of atmospheric factors

MARIANA ACHAD; MARÍA LAURA LÓPEZ; GUSTAVO G. PALANCAR; BEATRIZ M. TOSELLI

Córdoba

Congreso; 16 Congreso Internacional de Fotobiología; 2014

The most energetic solar radiation (the shortest wavelengths) reaching the Earth?s surface is in the UV range. This interval is responsible of producing measurable effects on biological systems affecting aquatic life and human health [1]. Different action spectrums are used to quantify these effects. For example, McKinlay and Diffey (1987) [2] established the erythemal action spectrum, which represents the spectral response of human skin to sunburn. The solar radiation weighted with this spectrum is so called erythemal radiation (EUV, 280?400nm) and is affected by different factors such as solar zenith angle (SZA), clouds, aerosol optical depth (AOD) and total ozone column (TOC). Erythemal ultraviolet irradiance was recorded from 2000 to 2012 in Córdoba, Argentina. EUV values under cloudless conditions are simulated by a radiative transfer (TUV4.1) model [3]. These model estimations are tested against experimental measurements showing an excellent agreement (root mean square error around 10%). EUV radiation and TOC temporal evolutions show a negative relationship. The influence on EUV irradiance from clouds and SZA variability are the prevailing effects. However, for a given SZA and clear-sky conditions, the total ozone and AOD are the main factors. In order to quantify these effects, the radiation amplification factor (RAF) concept is introduced. The overall mean radiation amplification factor due to total ozone (O3) (RAFO3) shows that 1% decrease in total ozone results in an increase of 1.16±0.23% in the EUV irradiance. A similar analysis of the RAF due to AOD (RAFAOD) shows that on average, a 1% decrease in AOD forces an increase of 0.082±0.012% in the EUV irradiance. Thus, overall sensitivity of UV to ozone was estimated to be about thirteen times higher than to the aerosol.