General Circulation: An Introduction

Here we study the two main 'ingredients' that control the general circulation of the atmosphere:
  1. earth's rotation
  2. differential heating (i.e. warming of the equator, cooling of the pole)
In the tropics the Coriolis parameter is small and earth's rotation has a less profound effect than in middle-to-high latitudes where the Coriolis parameter is large.

We focus on both tropical (Hadley) and extra-tropical (eddying) circulation patterns. The Hadley circulation occurs at low latitudes (small rotation) and is axi-symmetric. The extra-tropical circulation (high rotation) is dominated by unsteady, non axi-symmetric motions familiar to us as weather systems. We study both regimes in the laboratory and using atmospheric data.

To set the scene, on the left below we see a view of the earth over the north pole showing swirling clouds associated with synoptic-scale weather systems. On the right we show a laboratory analogue of the weather systems in which an ice can induces a radial temperature gradient in a rotating tank of water. The presence of eddies in the tank, analogous to atmospheric weather systems, can be seen through the swirling dye patterns.

This EAPS project is supported by the National Science Foundation.