# Thermospheric Neutral Wind Measurements and Investigations across the African Region--A Review
## 5 Comparisons with HWM-14 Predictions  
The HWM is a standard climatologic empirical model of the horizontal thermospheric neutral wind, in both meridional and zonal directions, across the globe. [PERSON] et al. (1988) [20] developed the initial version using data limited to satellite observations from Dynamic Explorer 2 and Atmospheric Explorer. Thereafter, the model was greatly improved by including measurements from other instruments, e.g., FPIs, incoherent scatter radars, and additional satellite measurements [22; 32; 33]. The most recent version of the model is the HWM-14 (updated in 2014, and detailed by [PERSON] et al., 2015 [22]). It is this version of the model that was primarily used for comparisons and validations in the studies from the African region on which the present paper reports. These studies indicate that the HWM-14 is fairly accurate in predicting the meridional and zonal wind patterns at the locations of  
Figure 7: Zonal winds in Nigeria for March 2016 to January 2018. The blue plots represent the FPI measurements, while the black plots represent corresponding HWM-14 predictions. The vertical error bars indicate the standard deviations of the observations. Adapted with permission from Ref. [4]. 2021, [PERSON] et al. the FPI stations on the continent, but with some notable differences between the model predictions and the FPI observations. At the mid-latitude station of Morocco, the model accurately predicts the poleward motion of the winds in the early evening hours of the winter season. It also accurately predicts the decrease in the poleward magnitude, and eventual switch to equatorward direction, during the early evenings of the summer season [23; 26]. A notable disparity is that the model underestimates the equatorward wind magnitude by as much as 30 m/s, especially during the months of April and May. On the other hand, the model overestimates the equatorward wind magnitude by as much as 40 m/s during the months of September to November. During the months of July to September, the times of the peaks for the equatorward winds are observed to be earlier for the model than for the FPI measurements [23]. The HWM-14 prediction of the meridional wind pattern in South Africa is also fairly accurate. For example, the magnitudes of the HWM-14 meridional winds during the winter months are smaller than during the summer months, which is in agreement with the FPI measurements [13]. There are, however, substantial differences in the peak times and peak magnitudes predicted by the model, in comparison to the FPI measurements. For example, the HWM-14 overestimates the meridional winds by about 20 m/s during summer, especially at the beginning of the nights. The model predicts the peaks of the equatorward winds to occur later than those of the FPI measurements during winter. During the summer and September equinox, the model predictions of the peak equatorward winds occur much earlier than those of the FPI measurements. These time differences between the peaks of the HWM-14 and FPI equatorward winds are in the range of 2-5 h. It is important to highlight here that this same earlier prediction of the equatorward peak was noted in Morocco for similar months (July to September) [23]. The HWM-14 does accurately predict the eastward zonal winds during the evening hours prior to midnight, before turning westward in the later part of the night. The times for the eastward-to-westward turning of the zonal wind are also correctly predicted by the HWM-14 for most of the months (February-October). However, for the months of November to January, the model's predictions of the times for the eastward-to-westward turning were significantly earlier (\(\sim\)2 h). Other discrepancies in the zonal wind were noted in the hours before local midnight between the months of March and November, when the HWM-14 overestimated the eastward FPI winds by about 30 m/s. The HWM-14 also predicted the peak of the eastward wind to occur \(\sim\)3 h earlier than observed in the FPI data.