The PIs propose to use the Jicamarca MST Radar for studies of equatorial middle atmosphere dynamics. The focus will be on the wave motions forcing the large-scale equatorial circulations in the stratosphere, mesosphere, and lower thermosphere and on the seasonal and short-term variability of the forcing and responses. The PIs plan to emphasize vertical coupling and transports of energy and momentum. Finally, they will study the variability of gravity waves, tides, Kelvin waves, and mixed Rossby-gravity waves on both the consequences of cross-equatorial flows and the influences of extra-tropical planetary waves on the dynamics at large and small scales.