Comparison of measured and modeled UV spectral irradiance at the Izaña station based on LibRadtran and UVA-GOA models

Abstract

In this work we have compared UV spectral global irradiance measurements performed with the spectroradiometer Bentham DMT 300 (UIIMP, University of Innsbruck, Institute of Medical Physics Austria, ATI) and the simulations obtained with two radiative transfer models: UVA-GOA and LibRadtran. The measurements were performed on 1st June 2005, during the QASUME (Quality Assurance of Solar Ultraviolet Spectral Irradiance Measurements) intercomparison campaign at the Izana (Tenerife) observatory. The results of UVA-GOA model shows differences with experimental data between 50% and 70% for wavelengths lower than 320 nm, which decrease to 10% around 320 nm. For the LibRadtran model the differences range from 20% at 280 nm to 3%-5% at 320 nm. These differences, which are in the range of ozone absorption, are due to the simplified approach used in UVA-GOA to treat the absorption-transmittance. For the range between 320 nm and 400 nm, the differences are lower than 6% (i.e. within the experimental error) for the comparison between both models and the measurements.