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Madden-Julian Oscillation (MJO) Effects in the GOLD O/N2 and Swarm-C neutral density during 2018-2019?
  • Federico Gasperini,
  • Hanli Liu,
  • Quan Gan
Federico Gasperini
Atmospheric and Space Technology Research Associates, LLC

Corresponding Author:[email protected]

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Hanli Liu
National Center for Atmospheric Research
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Quan Gan
Laboratory for Atmospheric and Space Physics
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The extent to which terrestrial weather below 30 km in altitude can influence the dynamics and mean state of the thermosphere (ca., 100-500 km) is a fascinating discovery of the last two decades or so. Waves that are excited by deep convection in the tropical troposphere and propagate vertically into the thermosphere are responsible for much of this influence. Tropospheric convection associated with the Madden JulianOscillation(MJO), the dominant mode of intra-seasonal variability in tropical convection and circulation, has been known to modulate the intensity of upward propagating gravity waves and Kelvin waves. An MJO impact on tides was already proposed over two decades ago, but only recent gains in satellite observational capabilities allows one to quantify their effect from observations. Previous work by Gasperini et al. [2017a] demonstrate that a 90-day oscillation in tropospheric convection during 2009-2010 is imprinted on both thermospheric mean winds and the eastward propagating wavenumber 3 diurnal (DE3) tidal amplitudes observed by the GOCE and CHAMP satellites and modeled with the TIME-GCM. In a follow-on modeling-based study, Gasperini at al. [2020] present statistical evidence for a strong connection (+/-12%) between the phase of the tropospheric MJO and the amplitudes of the thermospheric DE3 and 3-day ultra-fast Kelvin wave (UFKW), two of the most prominent and well-established waves from the tropical wave spectrum that preferentially propagate into the thermosphere. These recent studies demonstrate that strong coupling between the troposphere and the thermosphere occurs on intra-seasonal timescales, raising important questions that have implications for the whole atmosphere system. In this work, we present evidence for a strong quasi-60 day oscillation in GOLD column-integrated O/N2 and Swarm-C total mass density during 2018-2019. A similar and concurrent oscillation is observed in the DE3 and SE2 tidal amplitudes derived from SD/WACCM-X. Spectral analysis of OLR reveals a similar oscillation in tropical tropospheric convection that is shown to be eastward propagating with s=-1 and is thus consistent with an MJO event.