Answer the following question given this paragraph: 

Earth is hottest at the equator and gets cooler toward the poles. The differences in heating create huge convection currents in the troposphere. At the equator, for example, warm air rises up to the tropopause. It can’t rise any higher, so it flows north or south.


Q: When warm air rises up to the tropopause, where does it flow?


A:
north or south