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

Abstract

Five years of atmospheric temperature data, collected with an Fe Boltzmann lidar by the University of Colorado group from 2011 to 2015 at Arrival Heights, are used to characterize the vertical wavelengths, periods, vertical phase speeds, frequency spectra, and vertical wave number spectra of stratospheric gravity waves from 30 to 50 km altitudes. Over 1000 dominant gravity wave events are identified from the data. The seasonal spectral distributions of vertical wavelengths, periods, and vertical phase speeds in summer, winter, and spring/fall are found obeying a lognormal distribution. Both the downward and upward phase progression gravity waves are observed by the lidar, and the fractions of gravity waves with downward phase progression increase from summer ~59% to winter ~70%. The seasonal and monthly mean vertical wavelengths and periods exhibit clear seasonal cycles with vertical wavelength growing from summer ~5.5 km to winter ~8.5 km, and period increasing from summer ~4.5 h to winter ~6 h. Statistically significant linear correlations are found between the monthly mean vertical wavelengths/periods and the mean zonal wind velocities from 30 to 50 km. Assuming horizontal phase speeds independent of month, the monthly mean horizontal wavelengths, intrinsic periods, and group velocities are estimated for stratospheric gravity waves. The slopes of wave frequency spectra change from −1.9 at 30–60 km to −1.45 around 60–65 km. The vertical wave number spectra show the power spectral density at vertical wavelengths of 5–20 km decreasing from winter maximum to summer minimum. Several aforementioned features are observed for the first time in Antarctica.

Effects of Horizontal Wind Structure on a Gravity Wave Event in the Middle Atmosphere Over Syowa (69°S, 40°E), the Antarctic

“…These results are consistent with the results from previous studies in the Antarctic region (Kaifler et al, 2015;Kogure et al, 2017;Liu et al, 2014;Zhao et al, 2017). This value increased by 2-3 times at each 10 km of altitude increase between 40 and 60 km altitudes, and the winter (June to August) mean values at each altitude were 2-3 times larger than those of the fall (March to April) and spring (October) periods.…”

The Excitation of Secondary Gravity Waves From Local Body Forces: Theory and Observation

“…This finding is in accordance with lidar observations at McMurdo at z = 30–50 km that found that followed lognormal distributions with respect to | λ z | and τ r (Zhao et al, ). That, as well as the fact that Zhao et al () observed GWs with both upward and downward phase progression, suggests that some of the GWs observed at McMurdo at z = 30–50 km were likely secondary GWs created in the stratopause region (i.e., z ∼ 40–65 km) by body forces from primary GW dissipation (Becker & Vadas, ). This conclusion is supported by a recent high‐resolution wintertime model study at McMurdo using the GW‐resolving KMCM (Vadas & Becker, ).…”

“…In this section we analyze two cases where fishbone structures are seen in temperature data measured by an Fe Boltzmann temperature lidar at Arrival Heights (166.69°E, 77.84°S) near McMurdo, Antarctica (Chu et al, ; Chu, Huang, et al, ; Chu, Yu, et al, ). For the cases shown here, we derive the temperatures from the pure Rayleigh scattering region at z ∼ 30–70 km using the Rayleigh integration technique (Alexander et al, ; Chu et al, ; Fong et al, ; Kaifler et al, ; Klekociuk et al, ; Lu et al, , ; Wilson et al, ; Yamashita et al, ; Zhao et al, ). All lidar data used here have 1‐hr temporal resolution and 1‐km vertical resolution.…”

Numerical Modeling of the Generation of Tertiary Gravity Waves in the Mesosphere and Thermosphere During Strong Mountain Wave Events Over the Southern Andes

“…Finally, several fishbone structures were identified in lidar data at McMurdo near the winter stratopause and were shown to contain secondary GWs (Vadas et al, ). As corroboration of these results, analysis of wintertime lidar data at McMurdo inferred that λ H of the GWs was much larger in the MLT than in the stratosphere (Chen et al, ; Chen & Chu, ; Zhao et al, ), in excellent agreement with model results (BV18; VB18).…”