Observations and fine‐scale model simulations of gravity waves over Davis, East Antarctica (69°S, 78°E)

Abstract

Large vertical velocities were observed throughout the troposphere at Davis, East Antarctica, on 18 February 2014 by a VHF wind‐profiling radar. Simulations using the Met Office Unified Model at 2.2, 0.5, and 0.1 km horizontal grid spacing were able to broadly capture the location, timing, and magnitude of the observed velocities, as well as reveal that they are due to small‐scale orographic gravity waves resulting from the interaction between the coastal topography and strong easterly winds associated with a synoptic‐scale cyclone situated to the north. The simulations indicated that the gravity waves are responsible for (i) temperature fluctuations which coincided with satellite‐observed cloud variations in the vicinity of Davis, suggesting that they have a crucial role in the formation of cirrus clouds, and (ii) large vertical momentum fluxes in the troposphere. The waves are prevented from propagating into the stratosphere by the background winds turning from near‐surface easterlies to lower stratospheric northerlies. As well as illuminating and quantifying the role that weather systems have in producing orographic gravity waves along the East Antarctic coastline, studies such as this should be exploited to improve the representation of key localized atmospheric processes in global climate models.

Inertia‐Gravity Waves Revealed in Radiosonde Data at Jang Bogo Station, Antarctica (74°37′S, 164°13′E): 1. Characteristics, Energy, and Momentum Flux

“…Various observational instruments have been used to investigate GWs over Antarctica, such as lidar (Innis et al, ; Yamashita et al, ), radar (Alexander et al, ; Fritts et al, ; Love & Murphy, ), superpressure balloons (Hertzog et al, , ), radiosondes (Innis et al, ; Moffat‐Griffin et al, ; Murphy et al, ; Pfenninger et al, ; Yoshiki et al, ; Yoshiki & Sato, ), all‐sky airglow imaging (Matsuda et al, ; Rourke et al, ), and satellites (Alexander et al, ; Jiang et al, ; Wu & Jiang, ). Among these, radiosondes have been actively employed for GW studies, as they can detect GWs at a wide range of vertical wavelengths for a long time period over various geographical locations.…”

Dynamical Drivers of the Local Wind Regime in a Himalayan Valley

“…Despite being less than 10 km apart, the vertical profiles at Namche and Pheriche show different patterns of acceleration components in the troposphere. Further analysis (not shown) suggests that this is likely due to small‐scale orographic gravity waves, which are trapped (e.g., Alexander et al, ) due to the background wind speed increasing with height, as is evident in Figures g–i. When averaged over the entire valley, the momentum budget components approach a quasi‐geostrophic balance between the Coriolis term and the pressure gradient term, although there is still a contribution from the advection term (Figures f and l).…”

An Introduction to Atmospheric Gravity Wave Science in the Polar Regions and First Results From ANGWIN

“…The lower atmosphere papers include another study of observations from Davis, this time focusing on lower atmosphere observations using a VHF wind profiling radar and comparing its observations with a high resolution version of the unified model (Alexander et al, ); the findings in this paper conclude that these lower atmosphere waves have an influence on the locally observed cirrus clouds. A climatological paper studying waves in the lower stratosphere above Halley (75°S, 26°W), Antarctica is also included in the collection, examining the variation in gravity wave properties throughout the year (Moffat‐Griffin & Colwell, ).…”