Temporal and Spatial Patterns of Interannual Variability of Total Column Ozone In Africa from Ground-Based Observations

Total Column Ozone (TCO) measured by the Dobson Spectrometer at Lagos, Nigeria (Lat. 6°27`N, Long 3°24`E) and Cairo, Egypt (30°03`N 31°15` E) has been analysed in this study. The results give the estimate of the long term annual and seasonal trends from January 1994-December 2004. It also provides statistics of means and variability on temporal and spatial scale. Using linear regression, results show that the TCO increases at an average of 1.34 DU/yr (or 0.50%/yr) in Lagos and 0.37 DU/yr (or 0.13%/yr) in Cairo. On the average an increase of 5.5 and 1.4% in tropospheric total column ozone was recorded in Lagos and Cairo, respectively during the eleven year period. The maximum deviation in daily variability of total column ozone were 38 DU (12.5%) and 91DU (23.9%) while the minimum deviation were -45DU (-20.1%) and -68.9DU (-31.0%), respectively for both Lagos and Cairo. The range of the seasonal change in Lagos represents 9.2% of the mean TCO value with maximum in August while its 12.1% in Cairo and maximum recorded in March.