Outline the main causes of air movement. Discuss the application and limitations of the tri-cellular model.
4.1.1b The Tri-cellular Model Miss Gaunt
2. (a) Outline the main causes of air movement.
One of the main causes of air movement is due to the pressure gradient force, which is the movement of air from high to low pressure areas. Between 38 degrees North and 38 degrees South of the equator there is a net surplus and towards the poles, a net deficit. Air then has to transfer from the low latitudes to high latitudes to balance the unequal heating. Coriolis and Centripetal forces also cause the movement of air. Coriolis force is the deflection of wind because of the Earths rotation, it doesn’t exist at the equator but increases towards the poles. The Centripetal force causes air moving in a deflected path to increase speed towards the centre of low pressure.
(b) Discuss the application and limitations of the tri-cellular model.
The tri-cellular model gives us a clearer indication on the reasons behind why climates vary between the equator and the poles. However, the model still has its limits as the positioning of the overhead sun changes causing seasonal shifts in the positions of high and low pressure areas. The model is very simplified because it only indicates North-South movement of energy. It also doesn’t take into account the middle latitudes of East-West air movement such as the jet streams and rossby waves that disrupt the Ferrel Cell.