The variability of nonmigrating tides detected from TIMED/SABER observations

This paper deals with the variability of the nonmigrating tides detected from the observation of the SABER instrument on board the TIMED satellite during the 11 year solar period from 2002 to 2012. The longitudinal wave number spectra with 1 day resolution were first estimated from the temperature data measured at the MLT altitudes (70-110 km) and at the lower midlatitudes and low latitudes (between ±45°). Then we used the wave number 4 component to obtain the nonmigrating tides in which the dominant component DE3 was further analyzed in detail. We found that the properties of the spatial distribution and large time scale variation of the DE3 component are similar to those of the previous works, which used the interpolated data with 2 month resolution. These properties are that the DE3 component occurs mainly at the low latitudes within ±30° and at the altitudes from 90 to 110 km; the tidal amplitude is larger during boreal summer and early autumn, smaller in spring and almost tends to disappear in winter; the component is slightly stronger during the eastward wind QBO phase than the westward phase. Practically, the higher-resolution data were used to reveal the day-to-day variability of the DE3 component. It is found that (1) the variability occurs mainly at the altitudes from 100 to 110 km with a peak at 106 km; (2) it is strong at the low latitudes and peaks around the equator, as well, slightly stronger in the Southern Hemisphere than in northern one; (3) it is considerably larger around solstitial months than equinoctial months; and (4) it would not experience an obvious interannual variation. The day-to-day variability of the DE3 component may be explained by the variance of the absolute amplitudes and the contribution of the wave phases, and the later seems to play more important role.