Planetary winds, also known as permanent winds, are winds that blow from high-pressure belts to low-pressure belts in the same direction throughout the year. They are controlled by the pressure belts located at the lower part of the atmosphere and blow towards the same direction throughout the whole year. Planetary winds are also called primary winds or prevailing winds and blow over a vast area of continents and oceans. There are three types of planetary winds:
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Trade Winds or Tropical Easterlies: These winds blow from subtropical high-pressure areas towards equatorial low-pressure areas and are noted for consistency in both force and direction. The zone of trade winds is called Hadley Cell.
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Westerlies: These winds move poleward from the sub-tropical high pressure in the northern hemisphere and are detected to the right and thus blow from the southwest. In the southern hemisphere, they are deflected to the left and blow from the northwest.
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Polar Easterlies or Polar Winds: These winds blow from polar regions towards sub-polar low-pressure regions. Their direction in the northern hemisphere is from northeast to southwest and from southeast to northwest in the southern hemisphere.
Planetary winds are called invariable or planetary winds because they involve larger areas of the globe and are distributed all over the globe. They are related to thermally and dynamically induced pressure belts and rotation of the earth. The location of the high and low-pressure belts is considered to be stationary on the globe, and winds blow from high-pressure belts to low-pressure belts.
