1. Walker Circulation

2. Mean Tropical Overturning Circulations
(Figure obtained from Introduction to Tropical Meteorology, 2nd Edition, © 2016 COMET.)

3. Base State Pacific Zonal Circulation
(Figure obtained from Introduction to Tropical Meteorology, 2nd Edition, © 2016 COMET.)

4. Base State Global Walker Circulation
(Figure obtained from Introduction to Tropical Meteorology, 2nd Edition, © 2016 COMET.)

5. Oceanic Transport z warming cooling W
Consider a 2-D fluid bounded by land masses to the west and east with temperatures decreasing with increased depth. Easterly winds at the surface of that fluid will attempt to carry the fluid westward. At the eastern edge of the fluid, it is replaced by cooler fluid from below. At the western edge, the fluid is forced downward. z
warming
cooling W
In reality, oceanic transport is far more complicated than in the simplistic diagram above. In particular, Ekman transport results in a ~45-90° rightward deflection (NH) of the oceanic transport vector, resulting in modest equatorial upwelling under easterly wind conditions. This becomes important when considering El Nino conditions.

6. Mean Daily Precipitation: Jan-Mar
Enhanced precipitation found to the west, especially with Pacific circulation and over South America.
Figures obtained using the freely-available NCEP-DOE Reanalysis II dataset.

7. Mean Daily Precipitation: Jul-Sep
Northward shift of enhanced precipitation occurs but still favors the western branches of the three major zonal circulations.
Other heating-induced features also contribute to precipitation patterns, as we will discuss later.
Figures obtained using the freely-available NCEP-DOE Reanalysis II dataset.

8. Linear Approximation: Walker Circulation
(Figure obtained from Introduction to Tropical Meteorology, 2nd Edition, © 2016 COMET.)

9. Linear Approximation: Walker Circulation
(u,v) - vectors
w - contours
(u,v) - vectors
p - contours
Meridionally-integrated flow
(Figure obtained from Gill (1980), © 1980 Royal Meteorological Society/Wiley Interscience.)

10. Linear Approximation: Hadley Circulation
zonal velocity
streamfunction
pressure perturbation
(Figure obtained from Gill (1980), © 1980 Royal Meteorological Society/Wiley Interscience.)