Geography Reference
In-Depth Information
Figure 1.2
Schematic representation of the major atmospheric circula-
tion cells and surface wind directions.
The polar cells tend to be weak as the Sun's energy is less intense
here.
Between the Hadley cell and the polar cell is the Ferrel cell. The
Ferrel cell consists of sinking air at around 30° north and south and
poleward-moving westerly winds at the Earth's surface. Rising air
occurs at the boundary between the Ferrel cell and the polar cell
and this is called the
Polar front
. At the surface within the Ferrel
cell are westerly winds carrying eastward moving cyclonic (anti-
clockwise) and anticyclonic (clockwise) circulation systems.
At higher levels in the troposphere the belt of prevailing west-
erly winds associated with the Ferrel cell is disturbed by large
undulations. There are generally between three and six large
atmospheric wave formations looping around the Earth known as
Rossby waves
. Imagine a dark spherical chocolate pudding on top
of which you have just poured some white liquid icing. The icing
will settle and solidify over the pudding to form a wavy boundary
