Lidar Observations of Stratospheric Gravity Waves From 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 2. Potential Energy Densities, Lognormal Distributions, and Seasonal Variations

Abstract

Five years of Fe Boltzmann lidar's Rayleigh temperature data from 2011 to 2015 at McMurdo are used to characterize gravity wave potential energy mass density (Epm), potential energy volume density (Epv), vertical wave number spectra, and static stability N2 in the stratosphere 30–50 km. Epm (Epv) profiles increase (decrease) with altitude, and the scale heights of Epv indicate stronger wave dissipation in winter than in summer. Altitude mean Etrue¯pm and Etrue¯pv obey lognormal distributions and possess narrowly clustered small values in summer but widely spread large values in winter. Etrue¯pm and Etrue¯pv vary significantly from observation to observation but exhibit repeated seasonal patterns with summer minima and winter maxima. The winter maxima in 2012 and 2015 are higher than in other years, indicating interannual variations. Altitude mean trueN2¯ varies by ~30–40% from the midwinter maxima to minima around October and exhibits a nearly bimodal distribution. Monthly mean vertical wave number power spectral density for vertical wavelengths of 5–20 km increases from summer to winter. Using Modern Era Retrospective Analysis for Research and Applications version 2 data, we find that large values of Etrue¯pm during wintertime occur when McMurdo is well inside the polar vortex. Monthly mean Etrue¯pm are anticorrelated with wind rotation angles but positively correlated with wind speeds at 3 and 30 km. Corresponding correlation coefficients are −0.62, +0.87, and +0.80, respectively. Results indicate that the summer‐winter asymmetry of Etrue¯pm is mainly caused by critical level filtering that dissipates most gravity waves in summer. Etrue¯pm variations in winter are mainly due to variations of gravity wave generation in the troposphere and stratosphere and Doppler shifting by the mean stratospheric winds.

Quasi‐Biennial Oscillation of Short‐Period Planetary Waves and Polar Night Jet in Winter Antarctica Observed in SABER and MERRA‐2 and Mechanism Study With a Quasi‐Geostrophic Model

“…The modeling results suggest a first‐order mechanism that the equatorial QBO affects the mean wind in the polar region and then alters the efficiency of extracting energy from the mean wind to generate EPWs, thereby imposing the QBO signal onto the polar EPWs. Chu et al () have shown that potential energy densities of stratospheric gravity waves observed at McMurdo, Antarctica, are larger in 2012 and 2015 winters than 2011, 2013, and 2014, which is opposite to EPW1 interannual variability. Such QBO‐like signature in gravity waves is likely caused by the filtering effect of the PNJ (X. Chu, private communication, 2019).…”

Lidar observations of large-amplitude mountain waves in the stratosphere above Tierra del Fuego, Argentina

“…However, a large-amplitude mesospheric mountain wave with 67 K peak-to-peak amplitude was observed by ground-based lidar for a short duration of 2 h above Lauder, New Zealand, which is also a gravity wave hot spot 35 , 36 . At southern high latitudes, intra-annual and seasonal gravity wave statistics are available from a number of lidar stations in Antarctica 22 – 25 . They all indicate increased gravity wave activity during winter, but likely do not capture the strongest events due to their location within the polar vortex.…”

“…Therefore, our lead question is: can local, continuous and high-temporal-and high-vertical-resolution observations of gravity waves in the lee of the Andes enhance our knowledge about the magnitude of the momentum that is deposited in the stratosphere? Such observations can be accomplished using powerful, vertically-pointing Rayleigh lidars as operated at few locations world-wide [21][22][23][24][25][26][27] . To specifically target the worlds's largest gravity waves, we installed the Compact Autonomous Rayleigh lidar (CORAL) at Rio Grande, Tierra del Fuego, Argentina, for night-time measurements of atmospheric temperature.…”

Orographic Primary and Secondary Gravity Waves in the Middle Atmosphere From 16‐Year SABER Observations

“…They propagate in all azimuths except perpendicular to the body force direction. For those that propagate upward, their amplitudes increase exponentially with height, thereby enabling them to have important influences on the upper atmosphere and ionosphere (Becker & Vadas, ; Bossert et al, ; Chu et al, ; de Wit et al, ; Fritts et al, ; Heale et al, ; Liu & Vadas, ; Vadas et al, ; Vadas & Becker, ; Vadas & Liu, , ; Watanabe & Miyahara, ; Zhao et al, ). Thus, it is important to characterize both the primary GWs and LSWs in both observations and model simulations.…”