## 2 Observations and Method for Data Analysis
### Climatology, Seasonal and Interannual Variability of the Nonmigrating Semidiurnal Tides  
The main features of the nonmigrating SW4 and SE2 tides will be presented by following the same pattern as that for the diurnal nonmigrating tides. These tides are actually the second and third strongest tides among all semidiurnal nonmigrating tides for the entire period of 21 years. Just for information, we will note that the strongest semidiurnal nonmigrating tide for the considered 21 years is the SW3 with climatologically mean amplitude slightly larger than 9 K. While the most probable excitation source of SW4 is the nonlinear interaction between the SPW2 and the migrating SW2 tide, that of the SE2 is the latent heat release associated with the 12 h variation in cumulus convection with zonal wavenumber 4 [11]. However, [PERSON] et al., 2009 [83], and to some degree verified by [PERSON] et al., 2011 [28], reported that the nonlinear interaction between DE3 and DW1 can also produce SE2. Figure 5a shows the climatologically mean (2002-2022) latitude-time structures of the SW4 (left plot) and the SE2 (right plot) tidal amplitudes (in Kelvin) calculated at altitude of 110 km. It is seen that the climatologically mean amplitudes of both tides are very close, 6.7 K for SW4 and 6.6 K for SE2. [PERSON] et al., 2014 [84], investigated the above-considered tides for 9 years (2002-2010), finding very similar to Figure 5a latitude-time structures at altitude of 110 km with the same for the two tides largest amplitudes of 6.4 K. Furthermore, the SE2 tide was studied by [PERSON] et al., 2010 [27], for only six full years (2002-2007) and the authors also obtained similar latitude structure to that in Figure 6a, with the largest amplitude of \(\sim\)6 K. Figure 6b presents the altitude-latitude structures of the tidal amplitudes (upper row of plots, in K) and phases (bottom row of plots, in degrees) of the above-mentioned semidiurnal tides arranged in the same way as in Figure 1a; SW4 is shown in February, while SE2 is shown in May. Both tides are vertically upward-propagating, and most probably reaching the largest amplitudes slightly above 110 km height. Figure 6 presents the latitude-time structures of the monthly mean SW4 (upper plot) and SE2 (bottom plot) tidal amplitudes at altitude of 110 km; the time, again, is the number of months started from January 2002. It is seen that, during the considered period of 21 years, the monthly mean SW4 tidal amplitude reaches 10.5 K, while that of SE2 is 8.9 K or these nonmigrating tides also have large contribution to the neutral dynamics of the lower thermosphere. Regarding the highlighting of the main seasonal components, it can be noticed that the SW4 in the NH reveals mainly AC, while in the SH, the SAC can be well-visible as well; a similar feature is seen for the SE2, i.e., the AC in the NH is larger than that in the SH. Figure 6 reveals the presence of interannual variations as well, and it is more evident in SW4, particularly around latitudes of 0-15\({}^{\circ}\) N.  
Figure 7a demonstrates quite large AM of SW4 amplitudes reaching \(\sim\)5.4 K; it is distributed between 30\({}^{\circ}\) N and 40\({}^{\circ}\) S, but the main AM amplitudes are centered at 15\({}^{\circ}\) N, over the equator and around 30\({}^{\circ}\) S. The largest amplitudes of the AC and SAC of SW4 are, respectively, 4.3 K and 3.2 K; while the distribution of the AC is located between \(\pm\)20\({}^{\circ}\), that of the SAC is centered around 20\({}^{\circ}\) N and 30\({}^{\circ}\) S. Considering the main seasonal components of SE2 (Figure 7b), it is right away evident that the AM (6.2 K), particularly in the NH, is significantly larger than the AC (3.9 K) and SAC (2.6 K) ones.