Winds have carried mariners across the seas since before
recorded time. They so affected early seafaring that ancient sailors personalized
them with names and built legends around them. And still today, of course, because
winds influence weather on both a local and global scale, they affect our everyday
existence.
Wind Belts
Great belts of wind encircle the Earth. These bands of
global winds and lulls are created by the uneven way in which the Sun heats the
Earth, and by the mixing of air between the equator and the poles. Winds follow
several general patterns within certain zones, or belts. The northeast trades and
the southeast trades blow between 15 and 30 degrees latitude, the westerlies between 45 and 60 degrees latitude,
and the polar northeasterlies and polar southeasterlies between 60 and 90 degrees
latitude.
Between the wind belts lie zones of still air - the horse
latitudes between 30 and 45 degrees latitude, and the equatorial doldrums, which
cover the area extending 15 degrees north and south of the equator. In the equatorial
latitudes, the Sun's rays are nearly perpendicular to the Earth's surface, while
in higher latitudes, the Sun's rays strike the Earth at an angle. The result is
a greater concentration of solar energy per unit area in the tropics than in
the polar regions, and therefore greater warming in the tropics.