International Journal of Physical Sciences Vol. 3(1), pp. 001-005, April 2015 ISSN 2331-1827 ©2015 Academe Research Journals

Full Length Research Paper

Inter-comparison of Dobson Ozone Spectrophotometer, Differential Optical Absorption Spectroscopy and Ozonesonde measurements over Nairobi

Ngaina JN*, Muthama NJ, Mutai BK and Opija FJ

Department of Meteorology, University of Nairobi, P.O. Box 30197 – 00100 GPO, Nairobi, Kenya.

*Corresponding author. E-mail: jngaina@gmail.com. Tel: +254726792701.

Accepted 29 September, 2015

Abstract

Declining ozone layer due to air pollution and climate change has significant impacts on human health. This study assessed similarity of observed total ozone measurements through inter-comparison of data from ground based ozone measuring instruments (Dobson Ozone Spectrophotometer (DOS), Differential Optical Absorption Spectroscopy (DOAS) and Ozonesonde). Root Mean Square Error (RMSE), percentage difference and BIAS were used. RMSE values of 3.1, 3.3 and 5 DU were found with a BIAS of -1.1, 0.3 and 3.5 DU for DOS/DOAS, DOS/Ozonesonde and DOAS/Ozonesonde respectively.  Percentage difference ranged between -4.8 and 5.2% for all ozone measurements. RMSE, BIAS and percentage difference results for all measurements were small, tolerable and thus comparable. Development of a rigorous validation methodology, recalibration and regular validation of ozone measuring instruments on a regular basis will increase reliability of these measurements. This will ensure that inter-comparison with observed data over long periods of time will be possible and thus establish long trends of total ozone column needed for planning and policy related to air pollution in the region.

Key words: Ozone, bias, root mean square error, percentage error.