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The response of the mesospheric migrating diurnal (DW1) tide to the Madden-Julian oscillation (MJO) is investigated for the first time using a simulation from the Specified-Dynamic Whole Atmosphere Community Climate Model (SD-WACCM), which is driven by reanalysis data. Analysis shows that a significant connection exists between the MJO and the mesospheric DW1 tidal amplitude. During MJO phases 2 and 3, the convection anomalies are associated with enhancement in both the solar insolation absorption and latent heat release in the equatorial troposphere; these in turn lead to stronger DW1 forcing. Conversely, the forcing of DW1 by solar and latent heating in the troposphere is weaker during MJO phase 8. The difference of the tidal amplitude during the opposite MJO phases from the boreal winter mean state is similar to 15-20%. The parameterized gravity wave variations are found to have a significant impact on the DW1 tidal response in some phases of the MJO.

Plain Language Summary Atmospheric tides are global-scale variations in the meteorological variables (wind and temperature) that have a period of 1day or half of a day. They owe their existence to the daily variation in heating as the sunlight changes with local time. The wave pattern associated with the heating can propagate vertically. This wave grows with altitude and becomes very large in the altitude range of 80-100km above the Earth. This investigation explores how the amplitude of the largest tidal mode varies in response to a dominant tropospheric intraseasonal phenomenon known as the Madden-Julian Oscillation, or MJO, which is characterized by globally coherent variations in tropical convective activity with a time scale ranging from 30 to 90days. We investigated the possible influence of the MJO on the mesospheric diurnal westward propagating tide with zonal wavenumber 1 (DW1) using simulations in a whole-atmosphere model that is nudged to agree with analyses of observed meteorological data in the troposphere and stratosphere. The results of this investigation show that the amplitude of the atmospheric tide in the 80-100km altitude range varies as the MJO pattern evolves in time. Further analysis finds that this tidal variation is consistent with the current understanding of generation and dissipation of tides.