The Excitation of Secondary Gravity Waves From Local Body Forces: Theory and Observation Journal Article uri icon

Overview

abstract

  • AbstractWe examine the characteristics of secondary gravity waves (GWs) excited by a localized (in space) and intermittent (in time) body force in the atmosphere. This force is a horizontal acceleration of the background flow created when primary GWs dissipate and deposit their momentum on spatial and temporal scales of the wave packet. A broad spectrum of secondary GWs is excited with horizontal scales much larger than that of the primary GW. The polarization relations cause the temperature spectrum of the secondary GWs generally to peak at larger intrinsic periods τIr and horizontal wavelengths λH than the vertical velocity spectrum. We find that the one‐dimensional spectra (with regard to frequency or wave number) follow lognormal distributions. We show that secondary GWs can be identified by a horizontally displaced observer as “fishbone” or “>” structures in z − t plots whereby the positive and negative GW phase lines meet at the “knee,” zknee, which is the altitude of the force center. We present two wintertime cases of lidar temperature measurements at McMurdo, Antarctica (166.69°E, 77.84°S) whereby fishbone structures are seen with zknee=43 and 52 km. We determine the GW parameters and density‐weighted amplitudes for each. We show that these parameters are similar below and above zknee. We verify that the GWs with upward (downward) phase progression are downward (upward) propagating via use of model background winds. We conclude that these GWs are likely secondary GWs having ground‐based periods τr=6–10 hr and vertical wavelengths λz=6–14 km, and that they likely propagate primarily southward.

publication date

  • September 16, 2018

has restriction

  • bronze

Date in CU Experts

  • January 26, 2019 10:05 AM

Full Author List

  • Vadas SL; Zhao J; Chu X; Becker E

author count

  • 4

Other Profiles

International Standard Serial Number (ISSN)

  • 2169-897X

Electronic International Standard Serial Number (EISSN)

  • 2169-8996

Additional Document Info

start page

  • 9296

end page

  • 9325

volume

  • 123

issue

  • 17