Observations and model calculations of direct solar UV irradiances in the Schirmacher region of east Antarctica

Measurements of direct UV irradiances (using a MICROTOPS II Sunphotometer) carried out from a high-latitude site, Antarctica are presented. The instantaneous irradiances at 305 +/- 0.9, 312 +/- 0.9 and 320 +/- 1.0nm during a no-ozone-hole (13 December 2004) and an ozone-hole (4 October 2004) period have been observed to be about 0.031, 0.150 and 0.299Wm(-2) and 0.010, 0.049 and 0.102Wm(-2), respectively at local noontime. The observations of the direct UV irradiances at 305 +/- 0.9, 312 +/- 0.9 and 320 +/- 1.0nm are compared with tropospheric ultraviolet visible (TUV) radiation transfer model calculations. The model estimate shows that, during the ozone-hole period, a loss of ozone of the order of 44% leads to an increase in irradiance of the order of 410%, 90% and 25% at 305 +/- 0.9, 312 +/- 0.9 and 320 +/- 1.0nm, respectively. The relationship between change in UV irradiance due to a change in column ozone is obtained using a TUV model and irradiances thus estimated from this relationship are found to compare well with the observed irradiances