The Zonal Walker Circulation

In addition to the mean meridional Hadley circulation, there also exist zonal overturning circulations that contribute to the meteorology and climatology of the tropics. Together, these overturning circulations are commonly referred to as the Walker circulation. In this section, we first explore the history and basic structure of the Walker circulation. Later, we reintroduce the shallow water equations to demonstrate how prescribed heating leads to equatorially-trapped Kelvin and equatorial Rossby waves that comprise the Walker circulation. In so doing, we tie these features back to the Hadley cell circulation and provide motivation for subsequent lectures on the El Niño Southern Oscillation and monsoons.