Short-Term Tidal Variability in the Mesosphere/Lower Thermosphere from SABER

Abstract:

The understanding of migrating and nonmigrating tidal propagation from the troposphere and stratosphere into the mesosphere/lower thermosphere and upper thermosphere has much improved over the past few years. Yet, space-borne diagnostics of tides from single satellites like TIMED are limited to > monthly mean averages because of the slow orbit precession and the resulting local solar time coverage. Ground-based observations and whole atmosphere models on the other hand strongly suggest a short-term tidal variability on the order of a factor of two within a few days. This paper attempts to address this challenge by presenting a different approach than the conventional wavenumber/frequency Fourier fits to the satellite data: tides are diagnosed from the vertical/longitudinal structure of ascending-descending orbit node differences. This so-called “tidal deconvolution” method is applied to SABER temperature observations over one solar cycle. The resulting diurnal amplitudes and phases have an effective time resolution of approximately one week and are compared to short-term tidal diagnostics based on Fourier fits to multiple satellites and results from the NOGAPS-ALPHA, WACCM and eCMAM30 models for various tidal components. Preliminary results suggest that tidal components forced by tropical convection respond strongly to convective precipitation changes associated with the Madden-Julian-Oscillation while other nonmigrating tides show clear signatures of wave-wave interaction.