Dynamics of the Equatorial Mesosphere Observed Using the Jicamarca MST Radar during June and August 1987

Abstract

The Jicamarca MST radar was used in two campaigns during June and August 1987 to measure wave influences, flow variability, and mean structure in the equatorial stratosphere and mesosphere. This paper presents observations of motions and momentum fluxes in the mesosphere during each campaign. A companion paper by Hitchman et al. addresses the mean structure and fluxes as well as comparisons with other datasets. Results presented here indicate that the equatorial mesosphere is dynamically very active, with considerable gravity-wave and tidal motions and persuasive evidence of inertial instability and wave-filtering processes. Vertical velocities at high frequencies are comparable to those observed at other locations. Hourly mean horizontal motions and momentum fluxes are likewise large and variable, exhibiting enormous vertical shears and strong modulation of the wave spectrum and momentum fluxes at higher frequencies. Daily mean profiles reveal persistent structures with vertical scales of ?6?10 km, vertical shears of the meridional velocity of ?0.03 s?1, and large mean momentum fluxes. Also discussed are the implications of these observations for wave forcing and instability in the equatorial middle atmosphere.