Figure 5.6 The circulation of air in Hadley cells. In this example, the Sun is directly over the equator, as happens during the March and September equinoxes. At the latitude receiving the most direct sun, a column of warm air rises and the intertropical convergence zone (ITCZ) drops its precipitation. After rising more than 10 km into the atmosphere, the now cool, dry air circulates back to Earth at approximately 30° N and 30° S latitudes.