We show that the principal modes of variability of the near equatorial upper tropospheric flow, i.e. the annual march, ENSO and the MJO, all involve fluctuations back and forth between two states: a "perturbed state" characterized by heavy rainfall over the marine continent and an associated equatorially symmetric juxtaposition of equatorially trapped Kelvin and Rossby-waves, and a "relaxed state" characterized by relatively light rainfall over this region and relatively uniform geopotential height and weak winds over the entire tropics.
We examine the three-dimensional structure of the perturbed state and make reference to the solution to a steady state flow in a nonlinear shallow water wave equation on an equatorial beta-plane, forced by an idealized near equatorial heat source.
The Indo-Pacific region is also of special interest with respect to troposphere-stratosphere exchanges. The tropical pattern in its perturbed state seems to be playing an important role in this process.