Equatorial wave dynamics and their role in affecting tropical climate
Weiqing Han
Program In Atmospheric and Oceanic Sciences, CU Boulder
Equatorial waves are a set of free-wave solutions to the equations of
motion, under equatorial beta-plane approximation. On
intraseasonal-to-interannual timescales, the available waves are:
Kevin, Rossby, and mixed Rossby-gravity (or Yanai) waves. Each wave has
its distinct spatial structure and energy propagation. They can be excited
by surface wind stress that exerts on the ocean. The climatic importance
of these waves is that their evolution and propagation are associated
with the shoaling (or deepening) thermocline, which depicts equatorial
upwelling (or downwelling). Upwelling (downwelling)
processes can significantly alter the sea surface temperature (SST),
causing anomalous atmospheric response and thus impact tropical climate. The
well-known El Nino in the Pacific and the recently discovered Indian Ocean
Dipole Mode are all involve in equatorial wave processes.