Baseline Climatology of Gravity Waves From ∼30 to ∼70 km Established With Lidar Observations Over a Decade at McMurdo (77.84°S, 166.67°E), Antarctica: Implications for Vertical Wave Evolution
Journal Article
Overview
abstract
Abstract; Lidar observations of atmospheric gravity waves (GWs) have been made spanning 14 years above McMurdo Station, Antarctica. Using these extensive observations and interleaved data processing techniques which enable bias‐free/noise‐floor‐free estimation of GW parameters, this study forms seasonal baselines for GW potential energy densities (), ground‐based frequency () spectrum, and vertical wavenumber ( spectrum in the stratosphere (30–50 km) and mesosphere (50–70 km). The stratospheric is dominated by an annual oscillation with a winter maximum. Spring/fall profiles show decreased GW dissipation/breaking in 46–56 km. The wintertime profile shows two bending points, where the GW scale height steepens above 39 km and steepens further above 50 km. These bending points are scale dependent, where profiles with = 2–8 km bend only at 39 km, and profiles with = 8–30 km bend only at 50 km. GW ‐spectra from 30 to 50 km resembles 50–70 km ‐spectra at high‐ but differs at low‐, while frequency ‐spectra grows evenly over all . Spectral observations are examined in the context of linear instability, saturated cascade, and diffusive filtering theories, but the exact mechanisms responsible are to be determined. These bending points and spectral trends indicate consistent altitude ranges with enhanced GW dissipation. We propose that this dissipation could potentially serve as a source for the generation of secondary GWs in the middle atmosphere but the lidar data alone cannot confirm this, which deserves future study.
