Comparative Analysis of Total Ozone Data from Satellite EPTOMS and Ground-Based Dobson Instrument at Lagos-Nigeria

Abstract

This work represents a comparison study of total ozone data from the groundbased Dobson spectrophotometer and the overpass data from satellite instrument EPTOMS
in Lagos-Nigeria (Lat.6.6oN, Long 3.3oE) for the year 1997-2002. The result indicated that
EPTOMS ozone series overestimated those of the Dobson’s maximally between JulySeptember with an average difference of 11%, while the Dobson ozone profile exceeded
the EPTOMS by 6% in the month December-January. A strong anti-correlation of -0.88
was observed between the Dobson’s ozone profile and the EPTOMS in the month JulySeptember. The Dobson data showed considerable high frequency fluctuations with no
clear seasonal trend. Maximum inter-annual differences for both instruments fell within the
period of low precipitation in the West Africa region. Despite the monthly differences in
the two set of data, their seasonal and annual component showed significant positive
correlation of 0.53 with each other.