Dynamics Revealed from the High Correlation between the Mesospheric Summer Eastward Jet and the Phase Speed of a Decaying Quasi-2-Day Wave

This work uses simulations from the extended Canadian Middle Atmosphere Model (eCMAM) to show that the mesospheric summer eastward jet is highly correlated with the phase speed of a decaying quasi-2-day wave (Q2DW). 10 years of eCMAM simulations from 2000 till 2010 show statistically significant correlations of at least 0.9 between Q2DW and the mesospheric summer eastward jet specifically over an area between altitudes 50 km and 82 km and between latitudes 50S and 30S. Correlations are calculated between time-series of Q2DW phase-speed calculated from temperature fields and daily-mean zonal-mean zonal wind (UN). Their time-series spans 60 days after December solstice. The correlation is highest during the decaying phase of the Q2DW which is when the phase speed exponentially increases from around -70 m/s to -20 m/s. MLS observations of Q2DW phase speed in temperature also observes a similar progression although the exact day-to-day variability is different. Apart from being most correlated during the Q2DW’s decaying phase, the values of the phase speed and UN also become similar in range. A tendency analysis of the thermodynamic equation reveals that linear advection is a primary driver of Q2DW component of temperature. Also, of all classical and non-classical terms, the linear advection term's phase-speed is most similar with the temperature time-derivative term's phase-speed. This work therefore concludes that during the Q2DW’s decaying phase, Q2DW phase speed and UN exhibit a form of wave-mean flow unison because of the predominance of linear advection. This would suggest that the temporal evolution of Q2DW-induced longitudinal perturbations can be used to infer background zonal wind speeds.