Gravity Wave Activity in the Arctic Middle Atmosphere during the winters 2018-2022

The Rayleigh Temperature and Density Lidar (RDTL) installed at Poker Flat Research Range (PFRR) can measure high resolution densities and temperatures from 35 km to 85 km under nighttime conditions. The density fluctuations are later used to analyze the wave activity in the middle atmosphere using the noise-variance subtraction method. However, this limited gravity wave studies to altitudes below 55 km. To extend the studies to higher altitudes, the interleaved method is applied to the lidar data processing technique which allows to extend the analysis of wave activity in the 40-80 km region. In this study, we report Rayleigh Density and Temperature Lidar (RDTL) measurements of gravity waves activity in the 40-80 km region at Chatanika, Alaska (650 N, 1470 W) using the interleaved method. We use density profiles measured by the lidar to characterize gravity wave fluctuations. We consider both ensemble of waves as well as monochromatic waves. We present the wave activity from 76 nights in terms of specific potential energy over 10 km altitude ranges from 40 to 75 km. We find that the wave activity in the winter of 2018-2019 is reduced relative to the other winters. We discuss the propagation of wave energy with altitude. We analyze the correlation between gravity wave activity obtained from RDTL and horizontal winds. We characterize monochromatic gravity waves in terms of vertical wavelength and observed period from 51 nights where the observations length exceeded 8 hrs. We find 60 waves with periods between 2.0 and 7.7 hours, and vertical wavelengths between 5.7 and 21.8 km. We analyze these waves in terms of their stability.