Environmental Engineering Reference
In-Depth Information
winds in these areas allows a more effective transfer of energy between the tropics and
the polar regions.
POLAR EASTERLIES
Around the poles, beyond the main westerly belt, there is some evidence of prevailing
easterlies. The winds are variable and linked with the shallow polar anticyclones. In the
northern hemisphere they are often influenced by the circulation around the northern edge
of cyclones. As a result they change direction according to the local weather and
topography.
In the southern hemisphere the vast Antarctic ice cap controls the atmospheric
circulation around the pole. Anticyclones develop frequently over eastern Antarctica, and
strong south-easterly winds develop around the margins of the ice plateau with
consistencies similar to those of the trades, and occasionally of great strength.
UPPER WINDS
THE NATURE OF THE UPPER WINDS
Looking up at high clouds on a clear day, it is not unusual to find that the direction of
their movement is different from that of the surface winds. As this implies, winds in the
upper atmosphere can be affected by forces operating in a different direction from those
at the surface and may appear to be part of a different system of circulation. If we were to
make an ascent by balloon into these upper wind systems we would find that the change
from surface to upper atmosphere conditions was not abrupt but transitional. With
increasing height, we would discover, the winds tend to follow a gradually more distinct
zonal (east-west) direction and they become stronger. The main reason for this change is
the disappearance of the frictional influence of the ground surface upon the winds. In
other
