Equatorial Intraseasonal Temperature Oscillations in the Lower Thermosphere From SABER

Abstract

We analyze the spatial-temporal variability of the mesosphere/lower thermosphere (MLT) temperature at ±15N/S over 14 years, using measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument. We report that during the Madden-Julian Oscillation season (November–April) the MLT region exhibits temperature variations with dominant periodicities at 40 and 60 days with amplitudes as large as 5.0 K. These intraseasonal oscillations (ISOs) are expressed across all longitudes, having superimposed zonal wave-like structures that resemble waves 3 and 4 with amplitudes as large as 5.0 K. The cold and warm ISO phases are ubiquitous and repeatable from year to year over the 14-year satellite record. We show that the MLT ISO exhibits the characteristics of a propagating wave carrying the embedded zonal wave-like structures. At 20 km an ISO signal also exists with similar characteristics as the MLT ISO, suggesting a potential connection with the lower atmosphere.