## 4 Climatology (2002-2022) of Longitudinal Structures in the Lower Thermosphere
### SABER Temperature WN4 Structure  
In the context of the method applied in the present study for separating the tides from the SABER temperatures, described in detail by _[PERSON]_, 2023 [71], and the expression (2), in our case, \(k\) = 1, 2, 3, 4 while \(s\) changes from \(-\)4 to +4. The WN4 structure can be determined by \(\mid\)**s** + \(k\)\(\mid\) = 4. If the quarterdiurnal nonmigrating tides are excluded, then the WN4 structure can be generated by DE3, SE2, TE1 (T is for terdiurnal), and SPW4. Figure 9a shows the LT variability of the climatologically mean (2002-2022) SABER WN4 structure in August at different latitudes (they can be seen in the upper side of each plot); the uppermost plot reveals the structure over the equator, while the left and right column of plots demonstrates the NH and SH, respectively. We clarify that the climatologically mean WN4 structure signifies the superposition of the climatologically mean DE3 + SE2 + TE1 + SPW4. Figure 9a produces the WN4 structures at different latitudes only in August, not only because then the WN4 has the largest amplitudes (not at all latitudes), but also because such presentation provides the opportunity to trace how the LT dependence changes with the latitude, and also to shed a light on the hemispheric asymmetry during this month. The main features of the WN4 structure in the lower thermosphere (altitude of 110 km) can be summarized as: (i) in the latitudes of (0-10\({}^{\circ}\)) S the largest amplitudes of the WN4 structure (respectively 18.8 K and 20 K) are stronger than that of the DE3 (16.5 K, Figure 1); (ii) while at low and partly tropical latitudes, the WN4 structures show more than one enhancement at middle latitudes, and there is only one amplification; the observed enhancements reveal clear latitude dependence; (iii) at latitudes of \(\pm\)30\({}^{\circ}\) the WN4 structure almost disappears around 18 LT at 30\({}^{\circ}\) N and 11 LT at 30\({}^{\circ}\) S; this could be related to changes of the tidal contribution (for example, some decrease in the SE2 contribution); and (iv) while the WN4 structures at latitudes of (10-30\({}^{\circ}\)) S are stronger than those at (10-30\({}^{\circ}\)) N, at middle latitude (\(\pm\)50\({}^{\circ}\)) the opposite dependence is seen. It is worth noting that in the latitude bands of (10-30\({}^{\circ}\)) N(S), the largest WN4 amplitudes are observed in September (August), while in those of (40-50\({}^{\circ}\)) N(S) in March (November). Furthermore, considering the largest WN4 structures at all latitudes and months, the above-mentioned hemispheric asymmetry is still valid. We have made an attempt to assess the contribution of each nonmigrating tide and SPW4 during the months when the WN4 structure is strong. Figure 9b presents the latitudinal dependence of the tidal and SPW4 contribution to the WN4 structure in the months when it has large amplitudes; these are August (upper left plot), September (upper right plot), March (bottom left plot), and November (bottom right plot). These results confirm the already known features that the \"switched\" (\(\sim\)1000 km s\({}^{-1}\)) and \"switched\" (\(\sim\)1000 km s\({}^{-1}\)) are not consistent with the \"switched\" (\(\sim\)1000 km s\({}^{-1}\)) and \"switched\" (\(\sim\)1000 km s\({}^{-1}\)). Figure 9: (**a**) LT variability of the climatologically mean (2002–2022) SABER WN4 structure at different latitudes, shown in the upper side of each plot, during August; (**b**) latitudinal dependence of the tidal and SPW4 contribution in months when the SABER WN4 structure has large amplitudes: August (**upper left** plot), September (**upper right** plot), March (**bottom left** plot), and November (**bottom right** plot). the DE3 has the largest contribution to the WN4 followed by the SE2; the latter contributes the most in March and September, with a stronger contribution to the NH (we consider that the largest SE2 amplitude is observed at \(\sim\)40\({}^{\circ}\) N, Figure 5) than that to the SH. The third contributor is the TE1, while the SPW4 is the weakest one.