Hough Mode Decomposition of the DE3 tide extracted from TIMED observations

Abstract

Based on the daily DE3 temperature tidal component from Li et al. (2015), which is extracted from the TIMED/SABER observations in the mesosphere/lower thermosphere region (70–108 km altitudes) and at the low-latitude and mid-latitude (45°S–45°N) from 2002 to 2012, we decompose the 1-day resolution tidal component into some orthogonal Hough modes and the climatological (annual and inter-annual variations) and meteorological (day-to-day variability) characteristics of the first two ranks of the Hough modes are presented. The results show that the first four rank of the Hough modes can well reconstruct the latitudinal and altitudinal variation of the daily DE3 tidal component. Wherein, the first symmetric and antisymmetric Hough modes ((3, 3) ＆ (3, 4)) play an important role in the higher altitudes, meanwhile, the second symmetric and anti-symmetric Hough modes ((3, 5) ＆ (3, 6)) mainly contribute in the all altitude range, especially in the lower altitudes. The properties of the large time scale variation of the Hough coefficients are similar to those of previous work, which use the data with 60-day resolution. These properties are that the first symmetric Hough mode (3, 3) presents an obvious annual variation that they are stronger during boreal summer; the relative contribution of the first anti-symmetric Hough mode (3, 4) is much larger during boreal winter. Practically, the higher resolution data were used to reveal the day-to-day variabilities of the DE3 tidal Hough modes. It is found that the first two ranks Hough coefficients all dominate in high altitudes from 100 to 108 km and display an obvious semi-annual variation that they are larger in solstices than that in equinoxes. The day-to-day variability of each rank Hough coefficient may be explained by the variance of the absolute amplitudes and the contribution of the phases. It is found that the contribution from the absolute amplitudes plays an important role in the day-to-day variability of the first rank Hough coefficient; the contributions from the absolute amplitudes and phases are both important to the day-to-day variability of the second rank Hough coefficient.