Winds & Types ( Permanent or Planetary Winds & Local Winds )

Winds & their Types

Wind is the flow of gases on a large scale. On the surface of the Earth, wind consists of the bulk movement of air. Wind is caused by differences in atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the lower pressure area, resulting in winds of various speeds.

Types of winds ( Permanent or Planetary & Local )

• Prevailing or permanent or planetary winds
• Seasonal winds
• Local winds.

Permanent or Planetary Winds

• Winds blowing almost in the same direction throughout the year are called permanent or planetary winds.
• Trade winds, westerlies and polar winds are included under this category.

Trade winds

• The trade winds in the eastern margins of the oceans are drier than those in the western margin of the oceans because of the fact that the former comes into contact with the cold ocean currents.
• The zone of trade winds is called Hadley cell.

Westerlies

• These winds are best developed in 40-65 latitudes.
• In this zone of southern Hemisphere, because of lack of land masses and dominance of ocean, their velocity is so high that they become severely destructive & has been assigned special names based on the latitudes they flow through

• Roaring Forties (40 ) - at 40° latitude
• Furious Fifties (50 ) - at 50° latitude
• shrieking sixties (60 ) - at 60° latitude

Polar winds

• Due to very low temperature, the humidity bearing capacity of polar winds is very low.
• When these winds meet the westerlies in the sub-polar regions, polar fronts are developed and temperate cyclones are generated.

Seasonal Winds

Seasonal winds are movements of air repetitively and predictably driven by changes in large-scale weather patterns. Seasonal winds occur in many locations throughout the world. The name assigned to a particular seasonal wind and the underlying physical forces that drive the winds depend upon the unique geographic location.

One of the most commonly recognized seasonal winds are the monsoon winds. Although monsoons are often erroneously identified as rainstorms, they are actually a seasonal wind.

Local winds

Local winds are winds which cover smaller vicinity than global winds and usually possess some sort of peculiarity such as a higher pressure distribution than the global winds in the area.

Local terrain has a very strong influence on local winds, and the more varied the terrain, the greater the influence.

Chinook

• Chinook means the “Snow eater”.
• This is a hot and dry wind blowing along the eastern slope of Rockies and covers the area from the southern part of Colorado in the south to British Columbia in Canada in the North.
• Due to its effect, the snow melts and green grass sprouts even in the winter.
• This wind is helpful for the animal rearing as it makes the grassland snow free.

Foehn

• This is similar to Chinook and blows along the northern slope of the Alps.
• It affects the Switzerland most.

Black roller

• These are the warm and dry dusty winds, blowing in the great plains of North America.

Simoen

• This is the warm and dry wind blowing in the Arabian Desert.

Harmattan

• This is the warm and dry wind blowing from north-east and east to west in the Sahara desert.
• It is called ‘Doctor’ in the Guinea Coastal.

Norwester

This is the warm, dry and gusty wind blowing in northern New Zealand.