Attenuation by Clouds Over Abnormal UV Radiation Impact for Low Stratospheric Ozone Conditions

FACUNDO ORTE; RAUL D'ELIA; AKIRA MIZUNO; JACOBO SALVADOR; EDUARDO QUEL; ELIAN WOLFRAM; JONATHAN QUIROGA

Auckland

Simposio; International Radiation Symposium; 2016

International Radiation Commission (IAMAS, IUGG)

Stratospheric poor ozone air masses related to the polar ozone hole overpass subpolar regions in the Southern Hemisphere during spring and summer seasons, resulting in increases of surface Ultraviolet Index (UVI). The impact of these abnormal increases in the ultraviolet radiation could be overestimated if clouds are not taking into account. The aim of this work consist in determine the percentage of cases in which the cloudiness attenuate the high UV radiation that would reach the surface in low total ozone column situations and in clear sky hypothetical condition for Río Gallegos, Argentina. For these studies, it is analyzed the UVI obtained from a multiband filter radiometer GUV-541 (Biospherical inc.) installed in the Observatorio Atmosférico de la Patagonia Austral (OAPA) (51 º 33? S, 69 º 19? W), Río Gallegos, since 2005. The database used covers the period 2005-2012 for spring seasons. Measured UVI values are compared with UVI calculated using a parametric UV model proposed by Madronich (2007), which is an approximation for the UVI for clear sky, unpolluted atmosphere and low surface albedo condition, using the total ozone column amount, obtained from the OMI database for our case, and the solar zenith angle. It is observed that ~76% of the total low ozone amount cases, which would result in high and very high UVI categories for a hypothetical (modeled) clear sky condition, are attenuated by clouds, while 91% of hypothetical extremely high UVI category are also attenuated.