Equatorial Kelvin wave variability during 1992 and 1993

Temperature and ozone data from the Microwave Limb Sounder (MLS) instrument on UARS are used to analyze the variability of Kelvin wave activity during the first two years of the UARS mission. The analysis is carried out using the asynoptic mapping technique. Time frequency plots for zonal wavenumbers 1 and 2, at two heights representing the middle stratosphere and the stratopause, respectively, are used to analyze the temporal variability of the waves, and its possible relationship to the equatorial quasi-biennial oscillation (QBO) and semiannual oscillation (SAO). Kelvin wave activity reaches a maximum during the solstice seasons and almost disappears during the equinoxes, in agreement with previous studies. Eastward propagating variance is estimated for wave periods from 4 to 20 days, at all UARS pressure surfaces currently available for MLS. The semiannual modulation of variance is observed to extend down to the lower limits of the height ranges of the temperature and ozone retrievals. Furthermore, a superposed QBO modulation is detected up to the stratopause. Comparison between the variance in eastward propagating waves and the mean zonal wind shows a possible participation of kelvin waves in the forcing of the QBO. At the stratopause the role of Kelvin waves in forcing the SAO appears to be limited, in agreement with previous results. Between the 21-hPa and 4.6-hPa surfaces there appears to be a transition zone where there is no clear relationship between Kelvin wave activity and mean zonal flow acceleration.

[1]  Lucien Froidevaux,et al.  Equatorial Kelvin waves: A UARS MLS view , 1994 .

[2]  Richard Swinbank,et al.  A Stratosphere-Troposphere Data Assimilation System , 1994 .

[3]  B. A. Boville,et al.  A three-dimensional simulation of the equatorial quasi-biennial oscillation , 1992 .

[4]  B. Boville,et al.  Equatorial Waves in a Stratospheric GCM: Effects of Vertical Resolution , 1992 .

[5]  J. Gille,et al.  Kelvin wave variability in the upper stratosphere observed in SBUV ozone data. [SBUV (solar backscatter ultraviolet)] , 1991 .

[6]  J. Gille,et al.  Kelvin waves near the equatorial stratopause as seen in SBUV ozone data , 1991 .

[7]  R. Garcia,et al.  Chemical fluctuations associated with vertically propagating equatorial Kelvin waves , 1990 .

[8]  W. Randel.  Kelvin wave-induced trace constituent oscillations in the equatorial stratosphere , 1990 .

[9]  Kevin Hamilton,et al.  General Circulation Model Simulation of the Semiannual Oscillation of the Tropical Middle Atmosphere , 1988 .

[10]  C. Leovy,et al.  Estimation of the Kelvin Wave Contribution to the Semiannual oscillation. , 1988 .

[11]  L. Coy,et al.  Kelvin wave packets and flow acceleration: a comparison of modeling and observations , 1984 .

[12]  J. Gille,et al.  Evidence for Equatorial Kelvin Modes in Nimbus-7 LIMS , 1984 .

[13]  Murry L. Salby,et al.  Sampling Theory for Asynoptic Satellite Observations. Part II: Fast Fourier Synoptic Mapping , 1982 .

[14]  Murry L. Salby,et al.  Sampling Theory for Asynoptic Satellite Observations. Part I: Space-Time Spectra, Resolution, and Aliasing. , 1982 .

[15]  Isamu Hirota,et al.  Equatorial Waves in the Upper Stratosphere and Mesosphere in Relation to the Semiannual Oscillation of the Zonal Wind , 1978 .

[16]  G. D. Nastrom,et al.  Variations of Stratospheric Zonal Winds, 20-65 km, 1961-1971. , 1975 .

[17]  J. Holton,et al.  An Updated Theory for the Quasi-Biennial Cycle of the Tropical Stratosphere , 1972 .

[18]  J. Wallace,et al.  On the Interaction Between Kelvin Waves and the Mean Zonal Flow , 1971 .

[19]  T. Dunkerton.  On the role of the Kelvin wave in the westerly phase of the semiannual zonal wind oscillation , 1979 .

[20]  G. Cotton,et al.  A Climatological Analysis of Oscillations of Kelvin Wave Period at 50 mb , 1973 .

[21]  Yoshikazu Hayashi,et al.  A Generalized Method of Resolving Disturbances into Progressive and Retrogressive Waves by Space Fourier and Time Cross-Spectral Analyses , 1971 .

[22]  Y. E. Kousky.  On the Relation Between Kelvin Waves and the Quasi-Biennial Oscillation , 1968 .