Comparative study of short‐term diurnal tidal variability

Abstract

[1] The wind and temperature measurements from an unusually long period operation of the sodium lidar at Colorado State University (41°N, 105°W) around September equinox 2003 showed significant short-term tidal variability. Coincident with the large tidal changes, a strong temperature inversion layer was also observed above 90 km. Examination of the simultaneous temperature measurement from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, not only confirms the existence of the inversion layer but also reveals the global nature of the inversion, suggesting the presence of a transient planetary wave in the mesosphere. The large tidal variability, therefore, is probably a consequence of the interaction between the transient planetary wave and tides. This possibility is investigated by using the NCAR thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) and by comparing model results with the lidar, SABER, and TIMED Doppler Interferometer (TIDI) measurements. With a large transient planetary wave specified at the model lower boundary, the model is able to produce strong diurnal tidal variability comparable to that from the lidar observation, and the modeled temperature inversion is similar to that from the SABER measurement. The model results suggest that the planetary/tidal wave interaction excites nonmigrating tides and modulates the gravity modes and/or the rotational modes of the diurnal migrating tide. Among the nonmigrating tides, the diurnal zonally symmetric (S = 0) component is the strongest, and its interaction with the planetary wave leads to a strong diurnal eastward wave number 1 component.

Global Dynamics of the MLT

“…Such responses were seen by Liu et al (2007) in northern midlatitudes and Baumgaertner et al (2006) in the southern hemisphere.…”

WHU VHF radar observations of the diurnal tide and its variability in the lower atmosphere over Chongyang (114.14° E, 29.53° N), China

“…During the modulation, the amplitude of DT would vary with the periods of the PWs. There might be other possible mechanisms for the short-term variability of DT, e.g., the day-to-day variations in the mean wind (Merzlyakov et al, 2001), interactions with wave modes and gravity waves (Liu et al, 2007(Liu et al, , 2008, and tropospheric convective activity (Eckermann, 1997). However, the characteristic time of DT amplitude variation matching to the PW periods, together with bispectral analysis, confirms that the short-term variability of DT is at least partly caused by the interactions between DT and PWs.…”

Influence of gravity waves and tides on mesospheric temperature inversion layers: simultaneous Rayleigh lidar and MF radar observations

“…However, it may be noted that the diurnal tidal amplitude is significantly larger (40 m/s). Recently, Liu et al (2007) found that when diurnal and semi-diurnal tidal amplitudes increase by factors of 2-3, a strong temperature inversion was observed around 90 km. The authors suggested that the temperature inversions occurring in a global scale were probably as a consequence of tidal planetary wave interaction.…”