Lidar Observations of Instability and Estimates of Vertical Eddy Diffusivity Induced by Gravity Wave Breaking in the Arctic Mesosphere

On the night of 18–19 October 2018, sodium resonance lidar measurements show presence overturning in mesospheric layer. Two independent tracers, mixing ratio and potential temperature, derived from Rayleigh measurements, reveal that vertical spreading contours a layer convective instability coincide with this overturning. Analysis also reveals gravity waves propagate upward, are saturated, dissipate at height instability. The is analyzed terms turbulent diffusive transport using model based on material continuity sodium. Estimates eddy diffusion coefficient, K, energy dissipation rate, ε model. dissipated by calculated found to be sufficient generate turbulence. We consider three other examples overturning, nights of: 17–18 February 2009, 25–26 January 2015, 8–9 2018. For all four events we find values K (∼1,000 m2/s) larger (∼10–100 mW/kg) similar magnitude those typically reported ionization gauge measurements. These higher levels consistently regions lower stability.