WCD-08. Statistical Characterization of Persistent Gravity Waves in the Mesosphere and Lower Thermosphere at McMurdo, Antarctica With an Improved 2D Wavelet-Based Automatic Wave Recognition and Extraction Methodology

Abstract
Due to a combination of observational and modeling challenges, the behaviors and effects of gravity waves (GWs) in the upper atmosphere are still not well known. A new class of persistent GWs in the mesosphere and lower thermosphere (MLT) have recently been discovered via wintertime lidar observations at McMurdo Station, Antarctica (Chen et al., 2016; Chen and Chu, 2017). These waves appear to be present throughout each observation during the 10+ year McMurdo lidar campaign conducted by the University of Colorado Boulder and have amplitudes of ~20 – 30 K, indicating that they are capable of transporting significant amounts of momentum into the thermosphere - ionosphere system. It has been suggested that the majority of the waves are secondary GWs generated by the breaking of primary GWs in the stratosphere, of which observational evidence has recently been identified (Vadas and Becker, 2018; Vadas et al., 2018). Such secondary wave generation potentially plays a critical role in the complex, vertical coupling of the atmosphere by means of GWs. Therefore, systematic and statistical studies of the persistent GW properties and processes are necessary to understand the overall dynamic state of the upper atmosphere. To date, a 1-D wavelet transform has been used to characterize persistent wave properties during June using lidar data collected between 2011 – 2015 (Chen et al., 2016). Furthermore, Chen and Chu (2017) developed an automatic wave extraction methodology based on a corrected 2D wavelet transform, which was applied to three lidar observations taken in May, June, and July. For this study, modifications were made to this methodology in order to increase the robustness of the wave identification algorithm and enable a statistical study of the persistent waves. The application of this method to 10 years of McMurdo lidar data between 81 – 105 km will provide a reliable, observational baseline of GW properties in the MLT at high latitudes. Interpretation of trends in altitudinal profiles of vertical wavelength and phase speed will offer insight into the generation mechanisms and dissipation processes of the persistent GWs.