Observations of Inertial-gravity Waves Observed from Long-lasting Meteor Trail Echoes

Horizontal background wind in the mesosphere and lower thermosphere region of the Earth’s atmosphere deduced from the temporal displacement of a long- lasting meteor trail was estimated and investigated in this paper. The meteor trail echoes lasting more than 23 seconds in height range between 95 and 108 km as measured using the interferometry technique implemented at the Chung-Li 52 MHz radar, Chung-Li, Taiwan. The 3-meter electron density irregularities embedded in the meteor trail, which were responsible for the radar returns, were found without field-aligned property. Hodograph analysis reveals that the existence of an upward propagating inertia-gravity wave is associated with the vertical wavelength of 11.3 km. The wave-induced wind velocity and temperature perturbations combined with the background temperature profile of mass spectrometer and incoherent scatter (MSIS) model was used to estimate the height variation of the Richardson number (Ri). It is found that the feature Ri < 0.25 occurred in height range from 98 to 99 km, which implies that the wave is very likely broken in this height region through convective instability that was associated with negative temperature gradient induced by the gravity wave. The characteristics of echo power and spectral width associated with the wave-breaking turbulences are also discussed.