Nonlinear Interaction Between the Migrating Diurnal Tide and the Quasi-Two Day Wave

Details Nonlinear Interaction Between the Migrating Diurnal Tide and the Quasi-Two Day Wave Nonlinear Interaction Between the Migrating Diurnal Tide and the Quasi-Two Day Wave

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsa23a1771c&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #SA23A-1771

Physics

[3334] Atmospheric Processes / Middle Atmosphere Dynamics, [3337] Atmospheric Processes / Global Climate Models, [3369] Atmospheric Processes / Thermospheric Dynamics, [3389] Atmospheric Processes / Tides And Planetary Waves

Scientific paper

The migrating diurnal tide is one of the dominant dynamical features in the low latitudes of the Earth's Mesosphere and Lower Thermosphere (MLT) region, representing the atmospheric response to the largest component of solar forcing. Ground-based observations of the tide have resolved short term variations attributed to nonlinear interactions between the tide and planetary waves also in the region. Using the NCAR Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM), we simulate a quasi-two day wave (QTDW) event, known to attain large amplitudes in the post solstice periods. In this case, sideband sum and difference child waves are resolved, indicating that a nonlinear interaction is occurring between the QTDW and the tide. The migrating diurnal tide in the MLT displays local amplitude decreases of 20 - 40%, as well as a shortening of vertical wavelength by roughly 4 km. Examining the physical mechanisms driving the interaction, nonlinear advection is found to result in increased smoothing of the tidal structure when the QTDW is present in the MLT. Additionally, the QTDW also enhances the easterly summer mean wind jet that can also account for changes in tidal amplitude and vertical wavelength. We find that planetary wave induced background atmosphere changes can drive tidal variability at levels equal to or greater than nonlinear advection - a possibility not previously considered.

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