NASA Logo, External Link
Facebook icon, External Link to NASA STI page on Facebook Twitter icon, External Link to NASA STI on Twitter YouTube icon, External Link to NASA STI Channel on YouTube RSS icon, External Link to New NASA STI RSS Feed AddThis share icon

Record Details

Record 1 of 7023
Modeling the Observed QBO and Inter-Annual Variations of the Diurnal Tide in the Mesosphere
Author and Affiliation:
Mayr, Hans G.(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Mengel, John G.(Science Systems and Applications, Inc., Lanham, MD, United States)
Huang, F. T.(Creative Computing Solutions, Inc., Rockville, MD, United States)
Abstract: In the current version of the Numerical Spectral Model (NSM), the Quasi-biennial Oscillation (QBO) is generated primarily by small-scale gravity waves (GW) from Hines' Doppler Spread Parameterization (DSP). The model does not have topography, and the planetary waves are solely generated by instabilities. We discuss a 3D modeling study that describes the QBO extending from the stratosphere into the upper mesosphere, where the oscillation produces significant inter-annual variations in the diurnal tide. The numerical results are compared with temperature measurements from the SABER (TIMED) and MLS (UARS) instruments obtained by Huang et al. (2006). With a GW source that peaks at the Equator and is taken to be isotropic and independent of season, the NSM generates a QBO with variable periods around 26 months and zonal wind amplitudes of almost 25 m/s at 30 km. As reported earlier, the NSM reproduces the observed equinoctial maxima in the diurnal tide at altitudes around 95 km. The modeled QBO modulates the tide such that the seasonal amplitude maxima can vary from one year to another by as much as 30%. To shed light on the underlying mechanisms, the relative importance of the advection terms are discussed, and they are shown to be important in the stratosphere. At altitudes above 80 km, however, the QBO-related inter-annual variations of the tide are generated primarily by GW momentum deposition. In qualitative agreement with the SABER measurements, the model generates distinct zonal-mean QBO temperature variations in the stratosphere and mesosphere. In the stratosphere, the computed amplitudes are not much smaller than those observed, and the rate of downward propagation at the Equator is reproduced. The modeled temperature amplitudes in the mesosphere, however, are much smaller than those observed. The observed and computed temperature variations of the QBO peak at the Equator but extend with phase reversals to high latitudes, in contrast to the zonal winds that are confined to equatorial latitudes. Hemispherical asymmetries also appear in both the model results and the observations. The temperature amplitudes outside the equatorial region however tend to occur at lower latitudes in the model results. While there is qualitative agreement between the TIMED measurements and the model prediction, there are some areas of significant disagreement that require us to reexamine the present version of the NSM. The numerical results critically depend on the chosen parameters that determine the wave forcing, and there are a number of avenues to improve the performance of the model that had not been tuned to fit the observations. The GW spectrum and its latitude dependence in the troposphere are not well known, and numerical experiments are discussed that describe the related model response. While it appears that eastward propagating Kelvin waves and westward propagating Rossby gravity waves are not the primary source to generate the QBO, the GW forcing can seed the oscillation and act as a catalyst to enhance effectiveness of these planetary waves.
Publication Date: Jul 24, 2006
Document ID:
(Acquired Nov 28, 2008)
Document Type: Conference Paper
Meeting Information: Western Pacific Geophysics Meeting; 24 - 27 Jul. 2006; Beijing; China
Meeting Sponsor: American Geophysical Union; Washington, DC, United States
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Description: 1p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
Availability Source: Other Sources
Availability Notes: Abstract Only
› Back to Top
Find Similar Records
NASA Logo, External Link
NASA Official: Gerald Steeman
Site Curator: STI Program
Last Modified: August 24, 2011
Contact Us