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Title: Experiments on tropical stratospheric mean-wind variations in a spectral general circulation model

Abstract

A 30-level version of the rhomboidal-15 GFDL spectral climate model was constructed with roughly 2-km vertical resolution. This model fails to produce a realistic quasi-biennial oscillation (QBO) in the tropical stratosphere. Several simulations were conducted in which the zonal-mean winds and temperatures in the equatorial lower and middle stratosphere were instantaneously perturbed and the model was integrated while the mean state relaxed toward its equilibrium. The time scale for the mean wind relaxation varied from over one month at 40 km to a few months in the lower stratosphere. The wind relaxations in the model also displayed the downward phase propagation characteristic of QBO wind reversals, and mean wind anomalies of opposite sign to the imposed perturbation appear at higher levels. In the GCM the downward propagation is clear only above about 20 mb. Detailed investigations were made of the zonal-mean zonal momentum budget in the equatorial stratosphere. The mean flow relaxations above 20 mb were mostly driven by the vertical Eliassen-Palm flux convergence. The anomalies in the horizontal Eliassen-Palm fluxes from extratropical planetary waves were found to be the dominant effect forcing the mean flow to its equilibrium at altitudes below 20 mb. The vertical eddy momentum fluxes nearmore » the equator in the model were decomposed using space-time Fourier analysis. While total fluxes associated with easterly and westerly waves are comparable to those used in simple mechanistic models of the QBO, the GCM has its flux spread over a broad range of wavenumbers and phase speeds. The effects of vertical resolution were studied by repeating part of the control integration with a 69-level version of the model with greatly enhance vertical resolution in the lower and middle stratosphere. The results showed that there is almost no sensitivity of the simulation in the tropical stratosphere to the increased vertical resolution. 34 refs., 16 figs., 3 tabs.« less

Authors:
;  [1]
  1. Princeton Univ., NJ (United States)
Publication Date:
OSTI Identifier:
6721191
Resource Type:
Journal Article
Journal Name:
Journal of the Atmospheric Sciences; (United States)
Additional Journal Information:
Journal Volume: 49:24; Journal ID: ISSN 0022-4928
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; GENERAL CIRCULATION MODELS; EVALUATION; STRATOSPHERE; ATMOSPHERIC CIRCULATION; WIND; SIMULATION; EQUATOR; EQUILIBRIUM; FOURIER ANALYSIS; SPACE-TIME; TROPICAL REGIONS; EARTH ATMOSPHERE; MATHEMATICAL MODELS; 540110*

Citation Formats

Hamilton, K, and Yuan, L. Experiments on tropical stratospheric mean-wind variations in a spectral general circulation model. United States: N. p., 1992. Web. doi:10.1175/1520-0469(1992)049<2464:EOTSMW>2.0.CO;2.
Hamilton, K, & Yuan, L. Experiments on tropical stratospheric mean-wind variations in a spectral general circulation model. United States. https://doi.org/10.1175/1520-0469(1992)049<2464:EOTSMW>2.0.CO;2
Hamilton, K, and Yuan, L. 1992. "Experiments on tropical stratospheric mean-wind variations in a spectral general circulation model". United States. https://doi.org/10.1175/1520-0469(1992)049<2464:EOTSMW>2.0.CO;2.
@article{osti_6721191,
title = {Experiments on tropical stratospheric mean-wind variations in a spectral general circulation model},
author = {Hamilton, K and Yuan, L},
abstractNote = {A 30-level version of the rhomboidal-15 GFDL spectral climate model was constructed with roughly 2-km vertical resolution. This model fails to produce a realistic quasi-biennial oscillation (QBO) in the tropical stratosphere. Several simulations were conducted in which the zonal-mean winds and temperatures in the equatorial lower and middle stratosphere were instantaneously perturbed and the model was integrated while the mean state relaxed toward its equilibrium. The time scale for the mean wind relaxation varied from over one month at 40 km to a few months in the lower stratosphere. The wind relaxations in the model also displayed the downward phase propagation characteristic of QBO wind reversals, and mean wind anomalies of opposite sign to the imposed perturbation appear at higher levels. In the GCM the downward propagation is clear only above about 20 mb. Detailed investigations were made of the zonal-mean zonal momentum budget in the equatorial stratosphere. The mean flow relaxations above 20 mb were mostly driven by the vertical Eliassen-Palm flux convergence. The anomalies in the horizontal Eliassen-Palm fluxes from extratropical planetary waves were found to be the dominant effect forcing the mean flow to its equilibrium at altitudes below 20 mb. The vertical eddy momentum fluxes near the equator in the model were decomposed using space-time Fourier analysis. While total fluxes associated with easterly and westerly waves are comparable to those used in simple mechanistic models of the QBO, the GCM has its flux spread over a broad range of wavenumbers and phase speeds. The effects of vertical resolution were studied by repeating part of the control integration with a 69-level version of the model with greatly enhance vertical resolution in the lower and middle stratosphere. The results showed that there is almost no sensitivity of the simulation in the tropical stratosphere to the increased vertical resolution. 34 refs., 16 figs., 3 tabs.},
doi = {10.1175/1520-0469(1992)049<2464:EOTSMW>2.0.CO;2},
url = {https://www.osti.gov/biblio/6721191}, journal = {Journal of the Atmospheric Sciences; (United States)},
issn = {0022-4928},
number = ,
volume = 49:24,
place = {United States},
year = {Tue Dec 15 00:00:00 EST 1992},
month = {Tue Dec 15 00:00:00 EST 1992}
}