Lidar observations of persistent gravity waves with periods of 3–10 h in the Antarctic middle and upper atmosphere at McMurdo (77.83°S, 166.67°E)

Abstract

Persistent, dominant, and large‐amplitude gravity waves with 3–10 h periods and vertical wavelengths ~20–30 km are observed in temperatures from the stratosphere to lower thermosphere with an Fe Boltzmann lidar at McMurdo, Antarctica. These waves exhibit characteristics of inertia‐gravity waves in case studies, yet they are extremely persistent and have been present during every lidar observation. We characterize these 3–10 h waves in the mesosphere and lower thermosphere using lidar temperature data in June from 2011 to 2015. A new method is applied to identify the major wave events from every lidar run longer than 12 h. A continuous 65 h lidar run on 28–30 June 2014 exhibits a 7.5 h wave spanning ~60 h, and 6.5 h and 3.4 h waves spanning 40 and 45 h, respectively. Over the course of 5 years, 323 h of data in June reveal that the major wave periods occur in several groups centered from ~3.5 to 7.5 h, with vertical phase speeds of 0.8–2 m/s. These 3–10 h waves possess more than half of the spectral energy for ~93% of the time. A rigorous prewhitening, postcoloring technique is introduced for frequency power spectra investigation. The resulting spectral slopes are unusually steep (−2.7) below ~100 km but gradually become shallower with increasing altitude, reaching about −1.6 at 110 km. Two‐dimensional fast Fourier transform spectra confirm that these waves have a uniform dominant vertical wavelength of 20–30 km across periods of 3.5–10 h. These statistical features shed light on the wave source and pave the way for future research.

Modeled Gravity Wave‐Like Perturbations in the Brightness of Far Ultraviolet Emissions for the GOLD Mission

“…Since there are relatively few observations or modeling studies of this region, comparisons of this amplitude with other work are scarce. Our perturbations are somewhat smaller than those used by Hickey et al () and in line with the relative perturbations found by Chen et al () Becker and Vadas () for the 90–110 km altitude ranges.…”

Meteor radar observations of vertically propagating low‐frequency inertia‐gravity waves near the southern polar mesopause region

“…The λ z range of 14–28 km is highlighted. This λ z range is chosen based on Figures and and consistent with the previous studies on the southern polar mesospheric IGWs (16 km in Suzuki et al [], 22–23 km in Chen et al [], and 20–30 km in Chen et al []). For GWs with = 2| f |−3| f |, the GWs are expected to have the λ h s of about 400–1000 km.…”

“…Observed IGWs are in common characterized by near‐inertial intrinsic frequencies and large vertical wavelengths of more than 10 km. Chen et al [] analyzed in a rigorous and quantitative way the spectral characteristics of persistent IGWs with periods of 3–10 h observed at McMurdo, Antarctica, using lidar temperature in June for a period of 5 years. The persistent 3–10 h IGWs were found to have vertical wavelengths of 20–30 km and to be certainly differentiated from the global‐scale IGW modes (i.e., tidal waves), given that their vertical wavelengths are smaller than those of the high‐frequency tidal waves [ Smith et al , ; Du and Ward , ].…”

Lidar observations of stratospheric gravity waves from 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 1. Vertical wavelengths, periods, and frequency and vertical wave number spectra

“…Except for the frequency and vertical wave number spectra in section 5, for the studies in sections 3 and 4, all the data sets longer than 12 h are divided into 12 h observational segments without overlaps in order to ensure reasonable statistics on gravity wave parameters while including gravity wave spectra as much as possible. As the inertial period at McMurdo is 12.24 h and gravity waves with periods of 3–10 h are persistently observed in the MLT region [ Chen et al ., ], 12 h segments are the best choice of window size in our case. In this process of division, if the remaining segment at the end has observational length less than 6 h, then this observational segment is abandoned.…”

“…The following procedure is implemented to estimate the gravity wave perturbations. As the inertia‐gravity waves (IGWs) with periods of 3–10 h are persistent and dominant in the McMurdo MLT region [ Chen et al ., , ; Chen and Chu , ] while the planetary waves (PWs) are clearly seen in the stratosphere [ Lu et al ., ; Chen et al ., ], this procedure aims to keep the IGW spectra as full as possible but significantly filter out PWs and tides.…”