NWRA, Colorado Research Associates Division (CoRA), USA
University of Tokyo, Earth and Planetary Science, Japan
Penn State University, Center for Advanced Data Assimilation and Predictability Techniques, USA
Team members and participants
- Joan Alexander, NWRA, Colorado Research Associates Division (CoRA), USA
- Julio Bacmeister, National Center for Atmospheric Research, Boulder, CO USA
- Andrew Bushell, Met Office, Exeter, UK
- Naftali Cohen, Yale University, USA
- Stephen Eckermann, Naval Research Laboratory, Washington, DC USA
- Manfred Ern, Forschungszentrum Juelich, Germany
- Stephanie Evan, NOAA, Boulder, CO USA
- Marv Geller, State University of New York-Stony Brook, USA
- Kevin Hamilton, International Pacific Research Center, Honolulu, HI USA
- Albert Hertzog, LMD, L’Ecole Polytechnique, Palaiseau, France
- Takeshi Horinouchi, Environmental Earth Sci., Hokkaido University, Sapporo, Japan
- Yoshio Kawatani, Japan Agency for Marine-Earth Science, Yokohama, Japan
- David Long, University of Exeter, UK
- Peter Love, State University of New York-Stony Brook, USA
- Elisa Manzini, Max Planck Institute for Meteorology, Hamburg, Germany
- Charles McLandress, Dept. of Physics, University of Toronto, Canada
- Saroja Polavarapu, Environment Canada, Toronto, Ontario, Canada
- Peter Preusse, Forschungszentrum Juelich, Germany
- Manuel Pulido, Dept of Physics, Universidad Nacional del Nordeste, Argentina
- Fabrizio Sassi, Naval Research Laboratory, Washington, DC USA
- Kaoru Sato, Earth and Planetary Science, University of Tokyo, Japan
- Adam Scaife, Met Office Hadley Centre, Exeter, UK
- John Scinocca, Canadian Centre for Climate Modelling & Analysis, Victoria, Canada
- Tiffany Shaw, Columbia University, New York, NY USA
- Michael Sigmond, Environment Canada, Canada
- Robert Vincent, Dept of Physics, University of Adelaide, Australia
- Shingo Watanabe, Japan Agency for Marine-Earth Science, Yokohama, Japan
- Corwin Wright, Laoratoire de Physique des Oceans, Brest, France
- Nedjeljka Zagar, University of Ljubljana, Slovenia
Small-scale atmospheric waves, called gravity waves or buoyancy waves, have sources in the troposphere such as flow over topography, convection, and jet imbalance. As these waves propagate upward, they play an important role in atmospheric circulation at altitudes near the tropopause, and well above in the stratosphere and mesosphere. Interest in and understanding of these waves and their effects is progressing in tandem with increases in resolution in global atmospheric models; they are ubiquitous in observations and models that resolve them.
Global circulation models used for weather forecasting and climate prediction are beginning to resolve some of these waves, but the gravity wave sources in these models are poorly resolved (e.g. topography) or are parameterized processes (e.g. convection). Smaller scale gravity waves remain unresolved, yet are still quite important to global circulation. At issue are the strength and seasonal to interannual variations in zonal mean winds and temperatures that guide the propagation of planetary waves in the stratosphere or affect ozone chemistry. Models currently tune gravity wave drag parameterizations to adjust these winds and temperatures according to the needs of the particular model. For weather forecasting, for example, the strength of mid-latitude winds near the tropopause profoundly affects surface pressure anomaly patterns. Alternately, chemistry-climate models need realistic polar stratospheric temperatures to simulate ozone hole development. Parameterizations of gravity wave drag are crucial in simulating these processes.
Gravity wave parameterizations in many current models prescribe a simple set of parameters that control the circulation effects. These parameters have been poorly constrained in the past, but newer observations from satellites in particular provide global information over multiple years. Balloon, radar, and other observations remain important data sources as well. Combining these data with additional information provided by gravity-wave-resolving models is key to providing the global picture needed to understand the atmospheric state and any recent trends. This is one of the short-term goals of the SPARC Gravity Wave Activity.
Climate models eventually seek to relate wave generation and its effects on circulation to processes that evolve with changing climate. These require either extremely high horizontal and vertical resolution, or clear understanding of the processes that generate gravity waves and control variations. Comparisons of observations to parameterized waves in climate models and realistic gravity wave-resolving simulations is expected to lead to improvements in applications of existing parameterizations and/or new methods. This is a second goal of the SPARC Gravity Wave Activity.
In 2008, SPARC hosted a small group of scientists in Toronto with experience both in middle atmosphere climate modelling and in global observations of gravity wave momentum flux and drag to focus on the issue of how to improve the representation of gravity wave effects in climate models. A report on this meeting appeared in the July 2008 SPARC Newsletter (no. 31). The group involved in this first meeting also prepared a review paper (Alexander et al., 2010) on gravity wave effects in stratosphere-resolving climate models, recent observations, and analysis methods that reveal global patterns in gravity wave momentum fluxes, as well as results from some very high-resolution model studies capable of resolving gravity waves and their circulation effects.
Another team within the SPARC Gravity Wave Activity has begun an intercomparison of momentum fluxes associated with gravity waves in both observations and global models. The aim is not only to assess the degree of agreement among the various measures of momentum flux. We also plan to eventually merge existing global observations into a coherent set of constraints that may be applied either to gravity wave parameterizations in global models or to resolved gravity waves in present and future high-resolution model simulations. Early results show the strengths and weaknesses of current parameterization applications and may lead directly to improvements. Ongoing work is also providing new descriptions of the variability in gravity waves that may lead us toward new parameterization methods. The International Space Science Institute hosted the team’s meetings with additional support from SPARC/WCRP.
New work started in 2012 focuses on sources of gravity waves and the use of data assimilation methods to infer gravity wave forces on the circulation.
SPARC and the WCRP were also important supporters of the AGU Chapman Conference on Atmospheric Gravity Waves and Their Effects on General Circulation and Climate in Honolulu, USA, from 28 February – 4 March 2011. Co-conveners of the conference were Joan Alexander, Kevin Hamilton, and Kaoru Sato. 87 researchers around the world participated in sessions that included foci on the role of gravity waves in climate processes, observation methods and analysis results, and gravity wave resolving models on both regional and global scales. A description of the conference appeared in the July 2011 SPARC Newsletter No. 37.
de la Cámara, A. and F. Lott, 2015: A parameterization of gravity waves emitted by fronts and jets. Geophys. Res. Lett., 42, doi:10.1002/2015GL063298.
Plougonven, R., A. Hertzog, and M. J. Alexander, 2015: Case studies of nonorographic gravity waves over the Southern Ocean emphasize the role of moisture. J. Geophys. Res., 120, 1278-1299.
Sato, K. and M. Nomoto, 2015: Gravity wave-induced anomalous potential vorticity gradient generating planetary waves in the winter mesosphere. J. Atmos. Sci., 72, 3609-3624. doi: dx.doi.org/10.1175/JAS-D-15‐0046.1
Scheffler, G., and M. Pulido, 2015: Compensation between resolved and unresolved wave drag in the stratospheric final warnings of the Southern Hemisphere. J. Atmos. Sci., 72, doi: dx.doi.org/10.1175/JAS‐D-14‐0270.1
Geller, M.A., M.J. Alexander, P.T. Love, J. Bacmeister, M. Ern, A. Hertzog, E. Manzini, P. Preusse, K. Sato, A.A. Scaife and T. Zhou, 2013: A Comparison between Gravity Wave Momentum Fluxes in Observations and Climate Models. J. Climate, 26, No. 17, 6383-6405
Alexander, M. J., M. Geller, C. McLandress, S. Polavarapu, P. Preusse, F. Sassi, K. Sato, S. Eckermann, M. Ern, A. Hertzog, Y. Kawatani, M. Pulido, T. Shaw, M. Sigmond, R. Vincent, and S. Watanabe, 2010: Recent Developments on Gravity Wave Effects in Climate Models, and the Global Distribution of Gravity Wave Momentum Flux from Observations and Models. Q. J. Roy. Meteorol. Soc., 136, 1103-1124
SPARC activity updates:
SPARC Newsletter No. 44, 2015, p. 9: Gravity Wave Dynamics and Climate: An Update from the SPARC Gravity Wave Activity, M. Joan Alexander and Kaoru Sato.
SPARC Newsletter No. 37, 2011, p. 18: Report on the Chapman Conference on Atmospheric Gravity Waves and Their Effects on General Circulation and Climate, M. Joan Alexander, Kevin Hamilton, and Kaoru Sato.
SPARC Newsletter No. 35, 2010, p. 17: A report on the SPARC Gravity Wave Activity, M. Joan Alexander.
SPARC Newsletter No. 31, 2008, p. 6: New SPARC Project: Gravity Wave Momentum Budget for Global Circulation Studies, M. Joan Alexander.
SPARC Newsletter No. 28, 2007, p. 26: Report on the Gravity Wave Retreat, 26 June – 7 July 2006, Boulder, Colorado, USA, J. H. Richter, M. A. Geller, R. R. Garcia, H.-L. Liu, F. Zhang.
2016 SPARC Gravity Wave Symposium
16-20 May 2016
The Atherton Hotel and Pennsylvania State University, State College, Pennsylvania, USA.