Earth Planets Space, Vol. 51 (Nos. 7, 8), pp. 649-656, 1999
Anne K. Smith
Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO 80307, U.S.A.
(Received August 4, 1998; Revised February 12, 1999; Accepted February 12, 1999)
Abstract: This paper presents evidence for a quasi-stationary Kelvin wave of zonal wavenumber 1 that is forced in situ in the upper mesosphere and propagates upward from there. Although large scale quasi-stationary longitudinal variations are common in the mesopause equatorial winds, these variations often do not have a structure associated with a vertically propagating mode. However, during the periods of easterly winds that occur near the equinoxes in association with the mesopause semi-annual oscillation (MSAO), a Kelvin wave propagates away from the presumed altitude of forcing. The momentum transport by the Kelvin wave is small and does not make a significant contribution to the SAO wind evolution.