Introduction

There are two "ingredients" needed for weather on Earth:

1) Temperature Gradient

The Earth receives more sunlight at the equator than anywhere else. Hence, the equator receives the most net energy gain and loses the energy at the Poles. Temperature gradient is created through this process of the heat transfer. 

2) Rotation

Rotation can have an effect on the circulation of the atmosphere. In the tropics (Equator), the Coriolis force (due to rotation) is small, so the Earth's rotation has less effect on the tropics. On the other hand, Coriolis force has more effect in the the middle and higher latitudes. 

Hadley Circulation

The process of the gain and loss of solar heat sets up a general circulation pattern where the air rises near the equator, flows away from the equator until the 30 degrees latitude, sinks near the poles, and the flows back to the equator.This process is called Hadley Circulation. 

The air is not able to move beyond the 30 degrees latitude due to the conservation of angular momentum, especially the zonal velocity of the air must increase. The Coriolis effect is small. 

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(Source: http://www.cotf.edu/ete/modules/elnino/cratmosphere.html)

Eddies