Changes observed in sun photometer derived total column ozone and possible implications on surface-reaching UV radiation over a tropical Indian station

Abstract

Ozone depletion or unusual decreases in ozone content has now become a global issue because of the corresponding increases in surface reaching UV-B radiation. Sun photometer derived total column ozone along with that from Dobson spectrometer at a tropical urban Indian station, Pune (18°32′N, 73°51′E, 559 m Above Mean Sea Level) for the period 1998–2003 has been investigated. On a monthly mean scale the agreement between ozonometer and Dobson is within ± 3%. Ozone content at Pune during the winter months of January 1999 and 2002 were almost 6–7% lower than that observed during other years. This reduction in ozone content led to enhancement of erythemal dose at the surface during following summer months. Day-to-day variation on some occasions also showed ozone decreases accompanied by significant enhancement in surface reaching UV radiation. Optical remote sensing methods thus help to monitor unusual changes in ozone content.

Acknowledgements

The authors are grateful to the Director, Indian Institute of Tropical Meteorology, Pune for support and encouragement. Several research project students over the years contributed to the continuous sun photometer/ozonometer observational program at this station and this is gratefully acknowledged.