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Global Gravity Wave Variances from Aura MLS: Characteristics and InterpretationThe gravity wave (GW)-resolving capabilities of 118-GHz saturated thermal radiances acquired throughout the stratosphere by the Microwave Limb Sounder (MLS) on the Aura satellite are investigated and initial results presented. Because the saturated (optically thick) radiances resolve GW perturbations from a given altitude at different horizontal locations, variances are evaluated at 12 pressure altitudes between 21 and 51 km using the 40 saturated radiances found at the bottom of each limb scan. Forward modeling simulations show that these variances are controlled mostly by GWs with vertical wavelengths z 5 km and horizontal along-track wavelengths of y 100-200 km. The tilted cigar-shaped three-dimensional weighting functions yield highly selective responses to GWs of high intrinsic frequency that propagate toward the instrument. The latter property is used to infer the net meridional component of GW propagation by differencing the variances acquired from ascending (A) and descending (D) orbits. Because of improved vertical resolution and sensitivity, Aura MLS GW variances are 5?8 times larger than those from the Upper Atmosphere Research Satellite (UARS) MLS. Like UARS MLS variances, monthly-mean Aura MLS variances in January and July 2005 are enhanced when local background wind speeds are large, due largely to GW visibility effects. Zonal asymmetries in variance maps reveal enhanced GW activity at high latitudes due to forcing by flow over major mountain ranges and at tropical and subtropical latitudes due to enhanced deep convective generation as inferred from contemporaneous MLS cloud-ice data. At 21-28-km altitude (heights not measured by the UARS MLS), GW variance in the tropics is systematically enhanced and shows clear variations with the phase of the quasi-biennial oscillation, in general agreement with GW temperature variances derived from radiosonde, rocketsonde, and limb-scan vertical profiles.
Document ID
20100027386
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Wu, Dong L.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Eckermann, Stephen D.
(Naval Research Lab. Washington, DC, United States)
Date Acquired
August 24, 2013
Publication Date
December 1, 2008
Publication Information
Publication: Journal of the Atmospheric Sciences
Volume: 65
Subject Category
Physics (General)
Report/Patent Number
AD-A522432
XB-NRL/7600
Funding Number(s)
CONTRACT_GRANT: NNH04ZYS004N
Distribution Limits
Public
Copyright
Other
Keywords
MLS (MICROWAVE LIMB SOUNDER)
GW (GRAVITY WAVE)

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