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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.

Plain Language Summary We find that the Earth's temperature in the low-latitude mesosphere/lower thermosphere (MLT) region appears to increase and decrease by 5.0 K every 60 days. This behavior is present in every year from 2002 until 2016, and it affects all longitudes. Such an event was not possible before to observe, due to a limited number of ground-based stations that monitor the Earth's MLT region. In our analysis, we used satellite observations from 2002 to 2016 that covered all longitudes. The instrument we used was the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). Interestingly, superimposed within these intraseasonal oscillations (ISOs), the MLT region is noticed to also vary as a function of longitude. These variations represent waves that travel around the Earth's atmosphere increasing and decreasing the Earth's MLT region by 5.0 K. Interestingly, when such oscillations are present in the MLT region, the lower stratosphere presents similar variability at the same periodicities, which makes us to believe that there may be a potential influence of the lower to upper atmosphere. Our results provide a unique picture of the MLT's thermal structure as a function of longitude, which is important in model simulations of the dynamic structure of the MLT region.