HR: 1340h
AN: A43B-1154    [Abstracts]
TI: Gravity wave in the lower stratosphere at South Pole
AU: * Li, Z
EM: zli2@atmos.uiuc.edu
AF: Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, 105 S Gregory Street, Urbana, IL 61801, United States
AU: Robinson, W
EM: robinson@atmos.uiuc.edu
AF: Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, 105 S Gregory Street, Urbana, IL 61801, United States
AU: Liu, A Z
EM: liuzr@uiuc.edu
AF: Department of Electrical and Computer Engineering, University of Illinois at Urbana- Champaign, 1308 West Main Street, Urbana, IL 61801, United States
AB: Using high-resolution balloon soundings from 2001 to 2005, the relationship between gravity wave (GW) sources over Antarctica and the strength of GW activity in the lower stratosphere at South Pole (SP) are investigated. A comprehensive analysis is performed for the GW energy density, vertical wavenumber spectra, and stability. The seasonal variation of GW energy of three altitude sections (10-15 km, 15-20 km, and 20-25 km) are compared. GW perturbations in the lowermost section are strongest in May and September, whereas in the altitude range of 15-25 km, strongest GW energy is observed only in September, which indicates that the dominant GW sources for May and September at 10-15 km may be different. The relationship between the GWs and the synoptic-scale variations in the troposphere and ageostrophic motions in the upper troposphere are examined using correlation and empirical orthogonal function (EOF) analysis. The time series of EOF1 of these two significant mechanisms of GW generation both have a minimum in austral summer when GW energy is also minimized. A ray-tracing model is applied to explore the seasonal variation of GW propagation condition due to the background field. During the summer, it is harder for waves to propagate into SP from lower latitude. Thus the minimum of GW energy in austral summer is attributed to the combination of weaker generation from synoptic activity, geostrophic adjustment and unfavorable background field for GW propagation.
DE: 3349 Polar meteorology
DE: 3362 Stratosphere/troposphere interactions
DE: 3384 Acoustic-gravity waves
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting