Variability in Sun photometer–derived total ozone over a tropical urban station

Abstract

A portable, handheld, multichannel Sun photometer (ozonometer) has been used to measure total column ozone over Pune (18°32′N, 73°51′E, 559 m above mean sea level), India, a tropical urban station. Data collected on about 575 mostly clear‐sky days during the 5 year period from May 1998 to May 2003 have been used in this study to examine diurnal and seasonal variations. The overall daily mean total ozone at this station is 254 Dobson units (DU), with a variability of about 7%, while the most frequently occurring value is in the range 241–250 DU. The diurnal (daytime) patterns are observed to be different in the winter (December–February), premonsoon (March–May), and postmonsoon (October–November) seasons. There exists a predominant seasonal oscillation in total ozone, with higher values (265 DU) during premonsoon months and lower values (246 DU) during winter months. Ground‐based Sun photometer–derived total ozone variations compare very well with those obtained by Earth Probe‐Total Ozone Mapping Spectrometer.