A Note on the Interaction Between a Thermally Forced Standing Internal Gravity Wave and the Mean Flow, With an Application to the Theory of the Quasi-Biennial Oscillation

View More View Less
  • 1 National Center for Atmospheric Research, Boulder, CO 80307
© Get Permissions
Full access

Abstract

A numerical model of the interaction of the mean flow with a two-dimensional standing internal gravity wave was constructed. This model was similar to the quasi-biennial oscillation “analogue” model of Plumb (1977), except that it did not employ the WKB approximation and it included thermal excitation of the waves near the lower boundary (the wave forcing region extended over a region meant to correspond to the tropical troposphere). Calculations of the mean flow evolution in the model were performed with values of the wave parameters comparable to those appropriate for the equatorial waves which are believed to force the quasi-biennial oscillation in the real atmosphere. It was found that, when a realistic profile of mean flow dissipation was included, the results of these calculations in the portion of the model corresponding to the stratosphere were strikingly similar to those obtained with the original version of the Plumb model together with an artificial no-slip boundary condition imposed at the level of the tropopause. These calculations thus support the validity of the no-slip lower boundary condition which is used in current theoretical models of the quasi-biennial oscillation.

Abstract

A numerical model of the interaction of the mean flow with a two-dimensional standing internal gravity wave was constructed. This model was similar to the quasi-biennial oscillation “analogue” model of Plumb (1977), except that it did not employ the WKB approximation and it included thermal excitation of the waves near the lower boundary (the wave forcing region extended over a region meant to correspond to the tropical troposphere). Calculations of the mean flow evolution in the model were performed with values of the wave parameters comparable to those appropriate for the equatorial waves which are believed to force the quasi-biennial oscillation in the real atmosphere. It was found that, when a realistic profile of mean flow dissipation was included, the results of these calculations in the portion of the model corresponding to the stratosphere were strikingly similar to those obtained with the original version of the Plumb model together with an artificial no-slip boundary condition imposed at the level of the tropopause. These calculations thus support the validity of the no-slip lower boundary condition which is used in current theoretical models of the quasi-biennial oscillation.

Save