Comparative Study of the Variability of the Non-Migrating Tide DE3 Using WACCM-X Simulations and TIMED/SABER Observations

Based on the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) model outputs and Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations, we examine the global structures and temporal variations, that is, climatological and meteorological characteristics, of the daily diurnal eastward propagating non-migrating temperature tide with zonal wavenumber 3 component (DE3), which could drive the ionospheric longitudinal structure wavenumber 4 structure (WN₄), from 2003 to 2012 within the ±45° latitudes in the Mesosphere and low thermosphere (MLT) region (with altitude of 75–108 km). For the climatological characteristics (i.e., long-term variability such as inter- and intra-annual variations), both the WACCM-X model outputs and TIMED/SABER observations show that the DE3 tides have stronger amplitudes during boreal later summer and early autumn (July, August, and September), and show Quasi-biennial oscillation phenomenon. Meanwhile, only the WACCM-X model presents a weak peak of the DE3 in boreal winter (December, January, and February). As to the meteorological characteristics (i.e., short-term variability such as day-to-day variations), it is found that: (a) the short-term variabilities from both the model outputs and observations are stronger at low-latitudes (<30°) and high altitudes (>100 km); (b) the two datasets display an obvious semi-annual variation of the DE3 day-to-day variabilities with the monthly standard deviations larger during the solstices; (c) only from the WACCM-X model outputs, the short-term variability of the DE3 exhibit an annual variation with the monthly standard deviations larger in boreal winter, which is related to the small peak in the DE3 tidal amplitudes. Comparing the absolute amplitudes, the contribution of the wave phases play more important roles in the short-term variation of the temperature DE3 tidal component from both the WACCM-X model outputs and TIMED/SABER observations. Overall, the WACCM-X model outputs can well reproduce the temporal variation of the non-migrating tide DE3 in the MLT region, especially the day-to-day variability.