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

Abstract

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±1.0 nm 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 0.299 W m⁻² and 0.010, 0.049 and 0.102 W m⁻², respectively at local noontime. The observations of the direct UV irradiances at 305±0.9, 312±0.9 and 320±1.0 nm 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±1.0 nm, 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.

Acknowledgements

The authors are grateful to the National Center for Antarctic and Ocean Research, Goa for the logistic support. The authors are also thankful to the leaders of the 23rd and 24th Indian Scientific Expedition to Antarctica for providing the infrastructure for the experiment. We are also grateful to Sasha Madronich for the TUV model and valuable suggestions.