Abstract
An equatorial beta-plane model of the stratosphere is used to examine the effects of longwave radiational cooling, ozone photochemistry, and ozone advection on the linear spatial modulation of forced equatorial Kelvin waves. The model atmosphere is described by coupled equations for the zonal and meridional momentum, temperature, mass continuity, and ozone volume mixing ratio. For basic states characterized by a vertically sheared zonal wind that is in radiative–photochemical equilibrium, the linearized form of these equations is solved analytically and numerically. Results show that in the lower stratosphere, where the background vertical ozone gradient is positive, the wave amplitude is enhanced, whereas in the upper stratosphere, where temperature-dependent ozone photochemistry predominates, the wave amplitude is reduced. For vertical wind shears typical of the descending quasi-biennial oscillation (QBO) and semiannual oscillation (SAO) westerlies, it is shown that in the lower (upper) stratosphere the magnitude of the latitudinally integrated Eliassen–Palm flux, |<Fz>|, for an ozone modified Kelvin wave (OMKW) is 30% (40%) larger (smaller) than the corresponding unmodified Kelvin wave (UMKW) at a height of about 28 (50) km. For Kelvin waves of the lower (upper) stratosphere, the zonal body force per unit mass, measured by the divergence of |Fz|, shows that the OMKW drives the zonal mean circulation with more (less) acceleration than the UMKW above (below) 28 (50) km. Our results indicate that models that incorporate ozone feedbacks may be more successful in obtaining the proper phase and/or magnitude of the QBO and SAO at a particular height.
