Sources, sinks, and propagation characteristics of the quasi 6-day wave and its impact on the residual mean circulation

This study employs a troposphere to lower thermosphere assimilation model data set generated by the Whole Atmosphere Community Climate Model with data assimilation provided by the Data Assimilation Research Test Bed (WACCM+DART) to explore the sources, sinks, and propagation characteristics of the quasi 6-day wave (Q6DW) in the year 2007. WACCM+DART reproduces the burst-like Q6DW and compares well with Sounding of the Atmosphere using Broadband Emission Radiometry and Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics Doppler Interferometer observations.

The most prominent Q6DW took place in later February and mid-October, while the Q6DW was absent during solstice conditions in 2007. The occurrence of a large Q6DW in the equinoctial mesosphere and lower thermosphere is highly dependent on wave amplification and overreflection processes associated with barotropic/baroclinic instabilities and wave critical layers defined by the zonal mean zonal winds. During solstices, the winter hemisphere waveguide is negative and prevents the vertical wave propagation from the source region into the mesosphere and lower thermosphere.