Premium
Two‐Dimensional Model Studies of Equatorial Dynamics and Tracer Distributions
Author(s) -
Gray L. J.,
Pyle J. A.
Publication year - 1987
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711347611
Subject(s) - stratosphere , equator , solstice , westerlies , atmospheric sciences , oscillation (cell signaling) , mesosphere , climatology , kelvin wave , parametrization (atmospheric modeling) , quasi biennial oscillation , mesopause , forcing (mathematics) , gravity wave , geology , madden–julian oscillation , advection , momentum (technical analysis) , physics , latitude , meteorology , gravitational wave , astrophysics , convection , chemistry , geodesy , radiative transfer , biochemistry , quantum mechanics , thermodynamics , finance , economics
Abstract A parametrization of Kelvin wave absorption in the equatorial stratosphere has been included in a two‐dimensional model of the atmosphere in order to improve the simulation of the semi‐annual oscillation. Additionally, a more detailed treatment of the momentum deposition associated with gravity wave breaking in the mesosphere has replaced the previous Rayleigh friction scheme. the model exhibits a semi‐annual reversal of the zonal winds at the equator in the stratosphere, with the westerly phase descending with time, as observed. the inclusion of the improved gravity wave parametrization has led to a number of significant improvements; in particular, the model also exhibits a semi‐annual oscillation in the mesosphere which is out of phase with that in the stratosphere. Meridional circulations associated with the westerly phase of the semiannual oscillation produce ‘double peak’ structures in a number of modelled tracer fields, including N 2 O, CH 4 and H 2 O which compare well with observations by the SAMS and LIMS satellite experiments. These structures consist of a distinct minimum at the equator and double maxima in the subtropics; they are present for several months around each equinox. Inclusion of the more realistic westerly forcing has pointed to the need for additional easterly forcing in the model around each solstice. Further supporting evidence for the importance of momentum deposition associated with planetary waves in the easterly phase of the semi‐annual oscillation comes from the difference in double peaks between the northern hemisphere spring and autumn, as suggested in an earlier paper.