Effect of clouds on UV and total irradiance at Paradise Bay, Antarctic Peninsula, from a summer 2000 campaign

• Published in: Theoretical and applied climatology 2003-06, Vol.75 (1-2), p.105-116
• Main Authors: LUCCINI, E, CEDE, A, PIACENTINI, R. D
• Format: Article
• Language: English
• Subjects: Albedo; Cloud cover; Clouds; Earth, ocean, space; Exact sciences and technology; External geophysics; Fog; Meteorology; Radiative transfer. Solar radiation; Summer; Ultraviolet radiation
• ISSN: 0177-798X; 1434-4483
• DOI: 10.1007/s00704-003-0729-5

The analysis of ground-based measurements of solar erythemal ultraviolet (UV) irradiance with a Solar Light 501 biometer, and total (300-3000 nm) irradiance with an Eppley B pyranometer at the Argentine Antarctic Base "Almirante Brown", Paradise Bay (64.9 degrees S, 62.9 degrees W, 10 m a.s.l.) is presented. Measurement period extends from February 16 to March 28 2000. A relatively high mean albedo and a very clean atmosphere characterise the place. Sky conditions were of generally high cloud cover percentage. Clear-sky irradiance for each day was estimated with model calculations, and the effect of the cloudiness was studied through the ratio of measured to clear-sky value (r). Two particular cases were analysed: overcast sky without precipitation and overcast sky with rain or slight snowfall, the last one presenting frequently dense fog. Total irradiance was more attenuated than UV by the homogeneous cloudiness, obtaining mean r values of 0.54 for erythemal irradiance and 0.30 for total irradiance in the first case (without precipitation) and 0.27 and 0.17 respectively in the second case (with precipitation). Mean r values for the complete period were 0.58 for erythemal irradiance and 0.43 for total irradiance. Erythemal and total daily insolations reduce quickly at this epoch due to the increase of the noon solar zenith angle and the decrease of daylight time. Additionally, they were strongly modulated by cloudiness. Measured maxima were 2.71 kJ/m 2 and 18.42 MJ/m 2 respectively. Measurements were compared with satellite data. TOMS-inferred erythemal daily insolation shows the typical underestimation with respect to ground measurements at regions of high mean albedo. Measured mean total daily insolation agrees with climatological satellite data for the months of the campaign. [PUBLICATION ABSTRACT]