Investigation of the variability of night-time equatorial thermospheric winds over Nigeria, West Africa

This study examined the variability of the night-time equatorial thermospheric meridional and zonal wind speeds using an optical Fabry-Perot interferometer (FPI) located in Abuja, Nigeria (Geographic: 8.99 degrees N, 7.39 degrees E; Geomagnetic latitude: -1.60). The study period covered 9 months with useable data of 139 nights between March 2016 and January 2018. The hourly zonal wind speed is between -124 and 163 ms(-1) and that of the meridional wind ranged between -70 and 95 ms(-1). Comparison of FPI ground-based measurements with estimates from the Horizontal Wind Model (HWM-14) accurately reproduced the post-midnight meridional component, but for some departure of similar to 50 ms(-1) during pre-midnight. A very good agreement is observed between the predicted and measured zonal winds speed in the month of January 2018. However, the HWM-14 more often underestimated the zonal wind speeds in the months of 2016. Hence, this necessitates a call for improvement of the HWM-14 by using newly observed data in order to better characterize the West African sector. The varying zonal winds showed modal periods of 25.9 and 133.5 days, which are quasi 27 days and quasiterannual periodic variations, respectively. On the meridional wind, oscillatory periods of 133.5 and 23.1 days are seen in year 2016 and 2017, respectively.