Program Description

Gravity waves play an important role in the coupling of various atmospheric regions. Therefore, the study of gravity waves is a focal point of lower, middle, and upper atmospheric research, being of strong inter-disciplinary interest.

Gravity Wave Questions & Problems:

Initial testing of the Weather Research and Forecast model WRF) in the study of Gravity Waves. (J. Klemp, J. Dudhia, J. Richter, H.-L. Liu, A. Hassiotis, PSU)

There are outstanding questions in the gravity wave excitation mechanism, source distribution and variability, wave impact in the lower, middle and upper atmosphere, and parameterization of wave source and impact in global scale models. Flow over topography has been a classical example of gravity wave excitation and has been extensively studied. However, surface drag from orographic wave parameterizations in general circulation models is still problematic and hinders our ability to correctly resolve planetary waves in whole-atmosphere models.

Mesoscale modeling of gravity waves using realistic orography and weather condition and observations from campaign studies of orographic waves should be used to improve the quantification of the process. Gravity waves generated from realistic convective systems and from spontaneous adjustment due to geostrophic imbalance, as well as from complex interactions of these systems are still poorly understood and not well quantified. Petascale computing capabilities afforded by the upcoming NCAR Supercomputing Center will make possible high-resolution simulations of such systems, which will help to improve understanding of the gravity waves generated.

The gravity waves affect atmospheric processes in the lower, middle and upper atmosphere. The transport and deposition of momentum can affect the middle and upper atmosphere circulation, and wave breaking can generate turbulence that can affect aviation, constituents mixing, specifically mass exchange between upper troposphere/lower stratosphere and mesosphere/lower thermosphere, as well as heating and cooling in the upper atmosphere. Gravity waves may also affect space weather by seeding ionospheric irregularities.

The NCAR - University Opportunity

The vast spatial and temporal existence of gravity waves has important implications for the atmospheric dynamics and thermal/compositional structure from mesoscales to global scales. The multiscale nature of the gravity waves poses a stiff challenge to the physical understanding and quantification of these waves in both observations and numerical models. Integrated mesoscale modeling of these processes, extending from the wave sources to the impact region, is needed to address these problems. The integrated model can also support observational campaign studies of gravity waves as well as the validation of gravity wave parameterization. Such efforts will promote collaboration across the ESSL scientific divisions and between NCAR and the university community.

Satellite observations can provide valuable information on the global distribution and variability of gravity waves. The COSMIC radio occultation measurement is being used to derive the gravity wave variance and its global distribution and temporal variation. New algorithms will be explored to infer more specific gravity wave characteristics from COSMIC measurements. Data assimilation techniques will be tested to quantify global gravity wave impact by combining satellite observations of temperature, wind and WACCM simulations.

Program Lead - Contact

Dr. Hanli Liu
Email: liuh@ucar.edu
Phone: 303.497.1564

Dr. Jadwiga Richter
Email: jrichter@ucar.edu
Phone: 303.497.1564

Mailing Address: NCAR, P.O. Box 3000, Boulder, CO USA 80307-3000