Airborne observations of non-orographic gravity waves over the Southern Ocean: Tropospheric or Stratospheric Wave Excitation?

Andreas Dörnbrack* and Benedikt Ehard, Markus Rapp, David C. Fritts, Bifford P. Williams, Michael Taylor, Dominique Pautet, Stephen D. Eckermann, Ronald B. Smith, James D. Doyle
DLR Oberpfaffenhofen, Institute of Atmospheric Physics, Wessling, Germany

There are various different explanations of the belt of increased stratospheric temperature variances around 60°S surrounding Antarctica. Sato et al. (2012) highlighted the downstream propagation of mountain waves from the southern Andes and the Antarctic Peninsula but also admitted other non-orographic sources. Hendricks et al. (2014) concluded that primarily non-orographic tropospheric sources along the storm track might contribute to the observed enhanced temperature variances in the AIRS data. Alexander and Grimsdell (2013) investigate the role of small islands on the momentum deposition and found a significant stratospheric contribution. Most recently, Hindley et al. (2015) used GPS-radio occultation data to detect gravity waves in the SH stratosphere. Besides the above mentioned sources the authors report about a "zonal uniformity in the distribution of wave amplitudes" which might be "suggestive of strong, zonally uniform source mechanisms" around Antarctica and pointed to processes as "spontaneous adjustment or jet instabilities around the edge of the southern stratospheric jet".

Here, we report about unique airborne observations from the research flight RF25 of the NSF/NCAR GV during the DEEPWAVE campaign 2014 (Fritts et al., 2015). The in-situ and remote-sensing observations were conducted along two extended legs from New Zealand south to 63°S. They constitute the first observations in the stratospheric wave belt covering the troposphere and the middle atmosphere. Flight-level measurements as well as dropsonde, MTP measurements and radiosoundings from Macquarie Island indicate that the strong polar front jet excited gravity waves propagating into the stratosphere. On the other hand, the largest stratospheric temperature fluctuations in the range of 30 to 60 km altitude were observed by the airborne Rayleigh lidar south of the polar front jet directly in the vicinity of the polar night jet. The calculated gravity wave potential energy density peaks close to 60°S. All available data are compared to ECMWF operational analyses and the wave characteristics are retrieved from both data sets. The likely sources of the observed waves are determined and discussed in relation to existing theories.


Alexander, M. J. and Grimsdell, A. W.: Seasonal cycle of orographic gravity wave occurrence above small islands in the Southern Hemisphere: Implications for effects on the general circulation, J. Geophys. Res., 118, 11589-11599, doi:10.1002/2013JD020526, 2013.

Fritts, D. C, R. B. Smith, M. J. Taylor, J. Doyle, S. Eckermann, A. Dörnbrack, M. Rapp, B. P. Williams, P.-D. Pautet, K. Bossert, N. Criddle, C. Reynolds, A. Reinecke;. M. Udd¬strom, M. Revell, R. Turner, B. Kaifler, J. Wagner; T. Mixa, C. Kruse, A. Nugent, C. Watson, S. Gisinger, S. Smith. J. Moore, W. Brown, J. Haggerty, A. Rockwell, G.Stoss¬meister, S. Williams, G. Hernandez, D. J. Murphy, A. Klekociuk, I. M. Reid, Jun Ma, R. S. Lieberman, B. Laughman, 2015: The Deep Propagating Gravity Wave Experiment (DEEPWAVE): An Airborne and Ground-Based Exploration of Gravity Wave Propagation and Effects from their Sources throughout the Lower and Middle Atmosphere, Bull. Am. Meteorol. Soc., April 2015, accepted; doi:

Hindley, N. P., Wright, C. J., Smith, N. D., and Mitchell, N. J.: The southern stratospheric gravity wave hot spot: individual waves and their momentum fluxes measured by COSMIC GPS-RO, Atmos. Chem. Phys., 15, 7797-7818, doi:10.5194/acp-15-7797-2015, 2015.

Hendricks, E., Doyle, J., Eckermann, S. D., Jiang, Q., and Reinecke, P.: What Is the Source of the Stratospheric Gravity Wave Belt in Austral Winter? J. Atmos. Sci., 71, 1583-1592, doi:10.1175/JAS-D-13-0332.1, 2014.

Sato, K., Tateno, S., Watanabe, S., and Kawatani, Y.: Gravity Wave Characteristics in the Southern Hemisphere Revealed by a High-Resolution Middle-Atmosphere General Circulation Model., J. Atmos. Sci., 69, 1378-1396, doi:10.1175/JAS-D-11- 0101.1, 2012.

*Preference: Oral