HC 30 degrees 

On the equator heat rises and when it gets to the tropoclause it hits the tropoclause and reflects off to the side and rides the tropoclause till it gets to 30 degrees North and South it go's down at 30 degrees and heads back the equator. The cool air sinks at 90 degrees and runs along the earth then it hits 30 degrees and comes back to 90 degrees on the tropoclause.

heat rises up high                                  at the equator

rises at the equator                              heat rises up very high

of course it comes back                           and then it comes back