Editorial Type:
Article
Article Type:
Research Article

Diagnosing the QBO’s Influence on Circumpolar Vortex Variability Using MSU Brightness Temperatures and MSU-Derived Winds

Paul D. Reasor Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado

Search for other papers by Paul D. Reasor in
Current site
Google Scholar
PubMed Close
and
Michael T. Montgomery Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado

Search for other papers by Michael T. Montgomery in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Jan 1999
DOI:
https://doi.org/10.1175/1520-0493(1999)127<0046:DTQSIO>2.0.CO;2
Page(s):
46–56
Restricted access

Abstract

Using brightness temperatures from channels 3 and 4 of the Microwave Sounding Unit (MSU) as approximations to mean-layer temperatures, the geostrophic winds at 50 mb can be computed through a “bottom-up” approach. When this method is applied at high latitudes during austral winter and spring, it is found that accurate descriptions of the seasonal evolution and interannual variability of the lower-stratospheric circumpolar vortex are obtained. Variations in early-spring vortex strength from year to year appear to relate well to variations in the timing of the first large late-winter wavenumber one event in the lower stratosphere. Since wave forcing of the mean flow in the lower stratosphere is known to be weak, the variability in vortex strength may result from variations in wave-induced subsidence through the downward control principle.

Previous studies have demonstrated a biennial harmonic in both extratropical wave forcing and the mean flow, suggesting a link with the equatorially confined quasi-biennial oscillation (QBO). This study attempts to find a similar signal in the strength of the lower-stratospheric austral circumpolar vortex. It is first found that during the easterly (westerly) phase of the QBO large-amplitude wavenumber one in MSU channel 4, brightness temperature generally occurs earlier (later) in the season than normal. Subsequently, for most years of the study when the QBO is in its easterly (westerly) phase, the circumpolar vortex is observed to be weaker (stronger) than average.

Corresponding author address: Paul D. Reasor, Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371.

Email: reasor@eady.atmos.colostate.edu

Abstract

Using brightness temperatures from channels 3 and 4 of the Microwave Sounding Unit (MSU) as approximations to mean-layer temperatures, the geostrophic winds at 50 mb can be computed through a “bottom-up” approach. When this method is applied at high latitudes during austral winter and spring, it is found that accurate descriptions of the seasonal evolution and interannual variability of the lower-stratospheric circumpolar vortex are obtained. Variations in early-spring vortex strength from year to year appear to relate well to variations in the timing of the first large late-winter wavenumber one event in the lower stratosphere. Since wave forcing of the mean flow in the lower stratosphere is known to be weak, the variability in vortex strength may result from variations in wave-induced subsidence through the downward control principle.

Previous studies have demonstrated a biennial harmonic in both extratropical wave forcing and the mean flow, suggesting a link with the equatorially confined quasi-biennial oscillation (QBO). This study attempts to find a similar signal in the strength of the lower-stratospheric austral circumpolar vortex. It is first found that during the easterly (westerly) phase of the QBO large-amplitude wavenumber one in MSU channel 4, brightness temperature generally occurs earlier (later) in the season than normal. Subsequently, for most years of the study when the QBO is in its easterly (westerly) phase, the circumpolar vortex is observed to be weaker (stronger) than average.

Corresponding author address: Paul D. Reasor, Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371.

Email: reasor@eady.atmos.colostate.edu

Save
Cover Monthly Weather Review
Monthly Weather Review

  • Andrews, D. G., and M. E. McIntyre, 1976: Planetary waves in horizontal and vertical shear: The generalized Eliassen–Palm relation and the mean zonal acceleration. J. Atmos. Sci.,33, 2031–2048.

  • ——, J. R. Holton, and C. B. Leovy, 1987: Middle Atmospheric Dynamics. Academic Press, 489 pp.

  • Angell, J. K., and J. Korshover, 1964: Quasi-biennial variations in temperature, total ozone, and tropopause height. J. Atmos. Sci.,21, 479–492.

  • Baldwin, M. P., and K. K. Tung, 1994: Extra-tropical QBO signals in angular momentum and wave forcing. Geophys. Res. Lett.,21, 2717–2720.

  • Bowman, K. P., 1989: Global patterns of the quasi-biennial oscillation in total ozone. J. Atmos. Sci.,46, 3328–3343.

  • Dunkerton, T. J., and M. Baldwin, 1991: Quasi-biennial modulation of planetary-wave fluxes in the Northern Hemisphere winter. J. Atmos. Sci.,48, 1043–1061.

  • ——, D. P. Delisi, and M. P. Baldwin, 1988: Distribution of major stratospheric warmings in relation to the quasi-biennial oscillation. Geophys. Res. Lett.,15, 136–139.

  • Haynes, P. H., C. J. Marks, M. E. McIntyre, T. G. Shepherd, and K. P. Shine, 1991: On the “downward control” of extratropical diabatic circulations by eddy-induced mean zonal forces. J. Atmos. Sci.,48, 651–678.

  • Holton, J. R., and H.-C. Tan, 1982: The quasi-biennial oscillation in the Northern Hemisphere lower stratosphere. J. Meteor. Soc. Japan,60, 140–148.

  • ——, P. H. Haynes, M. E. McIntyre, A. R. Douglass, R. B. Rood, and L. Pfister, 1995: Stratosphere–troposphere exchange. Rev. Geophys.,33, 403–439.

  • Kinnersley, J. S., and K. K. Tung, 1998: Modeling the global interannual variability of ozone due to the equatorial QBO and to extratropical planetary wave variability. J. Atmos. Sci.,55, 1417–1428.

  • Manney, G. L., J. D. Farrara, and C. R. Mechoso, 1991: The behavior of wave 2 in the Southern Hemisphere stratosphere during late winter and early spring. J. Atmos. Sci.,48, 976–998.

  • Mechoso, C. R., D. L. Hartmann, and J. D. Farrara, 1985: Climatology and interannual variability of wave mean-flow interaction in the Southern Hemisphere. J. Atmos. Sci.,42, 2189–2206.

  • O’Sullivan, D., and R. E. Young, 1992: Modeling the quasi-biennial oscillation’s effect on the winter stratospheric circulation. J. Atmos. Sci.,49, 2437–2448.

  • Reasor, P. R., and M. T. Montgomery, 1996: Circumpolar vortex studies using MSU temperature data. Colorado State University Atmospheric Science Paper 619, 102 pp. [Available from P. Reasor, Dept. of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371.].

  • Shiotani, M., and I. Hirota, 1985: Planetary wave–mean flow interaction in the stratosphere: A comparison between Northern and Southern Hemispheres. Quart. J. Roy. Meteor. Soc.,111, 309–334.

  • ——, N. Shimoda, and I. Hirota, 1993: Interannual variability of the stratospheric circulation in the Southern Hemisphere. Quart. J. Roy. Meteor. Soc.,119, 531–546.

  • Spencer, R. W., and J. R. Christy, 1990: Precise monitoring of global temperature trends from satellites. Science,247, 1558–1562.

  • ——, and ——, 1993: Precision lower stratospheric temperature monitoring with the MSU: Technique, validation, and results 1979–1991. J. Climate,6, 1194–1204.

  • ——, W. M. Lapenta, and F. R. Robertson, 1995: Vorticity and vertical motions diagnosed from satellite deep-layer temperatures. Mon. Wea. Rev.,123, 1800–1810.

  • Tung, K. K., and H. Yang, 1994a: Global QBO in circulation and ozone. Part I: Reexamination of observational evidence. J. Atmos. Sci.,51, 2699–2707.

  • ——, and ——, 1994b: Global QBO in circulation and ozone. Part II: A simple mechanistic model. J. Atmos. Sci.,51, 2708–2721.

  • Vroman, T. T., and G. L. Stephens, 1989: Microwave brightness temperature and its relation to atmospheric general circulation features. Colorado State University Atmospheric Science Paper 454, 158 pp. [Available from G. Stephens, Dept. of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371.].

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 62 37 5
PDF Downloads 17 15 2