Influence of desert dust intrusions on ground-based and satellite- derived ultraviolet irradiance in southeastern Spain

[I] The desert dust aerosols strongly affect propagation of solar radiation through the atmosphere, reducing surface irradiance available for photochemistry and photosynthesis. This paper evaluates effects of desert dust on surface UV erythemal irradiance (UVER), as measured by a ground-based broadband UV radiometer and retrieved from the satellite Ozone Monitoring Instrument (aMI) at Granada (southern Spain) from January 2006 to December 2010. The dust effects are characteri zed by the transmittance ra tio of the measured UVER to the corresponding modeled clear sky value. The transmittance has an exponential dependency on aerosol optical depth (AOD), w ith minimum values of rvO.6 (attenuation of rv40%). The OMl UVER algorithm does not account for UV aeroso l absorption, which results in overestimation of the ground-based UVER especia lly during dust episodes with a mean relative difference up to 40% . The application of aerosol . absorption post-correction method reduces aMI bias up to "" 13%. The results highlight great effect of desert dust on the surface UV irradiance in reg ions like southern Spain, where dust intrusions from Sahara region are very frequent.