Effects of zonal wind on stratospheric ozone variations over Nigeria

Abstract

ABSTRACTThe effects of zonal wind on stratospheric ozone (O3) variation over Nigeria have been studied. The areas covered in this study include: Maiduguri (11.83° N, 13.15° E), Ikeja (6.45° N, 3.40° E), Port-Harcourt (4.75° N, 7.00° E), Calabar (4.95° N, 8.33° E), Makurdi (7.73° N, 8.54° E), Ilorin (8.50° N, 4.55° E), Akure (7.17° N, 5.08° E), Yola (9.23° N, 12.46° E), Minna (9.61° N, 6.56° E), Jos (9.93° N, 8.88° E), Kano (12.00° N, 8.52° E), and Enugu (6.45° N, 7.51° E), from 1986 to 2008. Zonal wind data was computed from the iso-velocity map employing Matrix Laboratory (MATLAB) software. The mean monthly variations of atmospheric angular momentum (AAM) and length of day (LOD) at pressure levels of 20, 30, and 50 mbar in the atmosphere mostly depict a trend of maximum amplitude between April and September, and minimum amplitude between December and March. The trend observed in seasonal variation of column ozone data in the low latitude had maximum amount from May through August and minimum values from December through February. The mean monthly maximum O3 concentrations was found to be 284.70 DU occurring at Kano (12.00° N, 8.52° E) in May 1989 while an average monthly minimum O3 concentration was found to be 235.60 DU occurring at Port-Harcourt and Calabar (4.75° N, 7.00° E and 4.95° N, 8.33° E, respectively) in January 1998. It has been established in this study that the variation in LOD caused by AAM mostly transfer O3 by means of zonal wind from the upper troposphere to the lower stratosphere in the stations under study. The strong effect of the pressure levels of the atmosphere on O3 variation could be attributed to its effect on the AAM and LOD. Variation in the LOD is significant in the tropics, suggesting that the effects of the extra-tropical suction pump action are not the only driver responsible for O3 transportation from the tropics to extra-tropical zones. Analyses show a relationship with strong correlation between rainfall intensities and total ozone throughout the year under study. For instance, the obtained value of r ranges between 0.676 and 0.957 and p-value <0.05. This most likely indicates that the phenomenon could probably contribute to total ozone variations in Nigeria. Consequently, these findings lead to a deduction that weather pattern alteration observed due to these changes could lead to climate change.