SOLAR ULTRAVIOLET IRRADIANCE AT TIERRA-DEL-FUEGO - COMPARISON OF MEASUREMENTS AND CALCULATIONS OVER A FULL ANNUAL CYCLE

A spectroradiometer located at Ushuaia, Tierra del Fuego, Argentina ob tained a high quality data set on the solar ultraviolet (UV) spectral irradiance for a full annual cycle during 1999. The unique aspect of t he ground-based irradiances is their ability to characterize the effec ts of cloudiness. Measured irradiances at 340 nm can be used to charac terize the attenuation provided by cloudy skies. When irradiances at s horter wavelengths, 302.5-320.0 nm, are adjusted for this attenuation, they show good agreement with radiative transfer calculations which a ssume clear skies and utilize data from the Total Ozone mapping spectr ometer (TOMS) as inputs. The differences which exist are qualitatively consistent with the neglect of spherical geometry in the calculated i rradiances.