Definition of Wind – The perceptible natural movement of the air, especially in the form of a current of air blowing from a particular direction.
Winds are commonly classified on the basis of spatial scale, their speed, the types of forces that cause them, the regions in which they occur, and their effect. List of some of the different types of winds are given below –
1. Planetary winds – Planetary winds constantly blow in the same direction all around the world throughout the year from one latitude to the other. They are also called prevailing or permanent winds. Example of Planetary winds are trade winds and the westerly winds.
2. Trade winds – Trade winds are found in the tropics in the lower section of the troposphere near the Earth’s equator. The trade winds blow predominantly from the north-east in the Northern Hemisphere and from the south-east in the Southern Hemisphere. Trade winds steer African dust westward across the Atlantic Ocean into the Caribbean Sea. The weaker the trade winds become, the more rainfall can be expected within neighbouring landmasses.
3. Westerlies – The westerlies are also known as anti-trades and prevailing westerlies. These winds are found in the in the middle latitudes between 30 and 60 degrees latitude, blowing from the high pressure area in the horse latitudes towards the poles. These prevailing winds blow from the west to the east. Westerlies are strong in the southern hemisphere where there is less land in the middle latitudes to cause the flow pattern to amplify. Due to their strong nature they are also known as Roaring Forties.
4. Polar winds – Polar winds blow from the polar high pressure to the sub polar low pressure area. In the northern hemisphere, they blow from the north-east. In the southern hemisphere, they blow from the south-east.
5. Doldrums – Doldrums are those parts of the Atlantic Ocean and the Pacific Ocean affected by the Intertropical Convergence Zone, a low-pressure area around the equator where the prevailing winds are calm. The low pressure is caused by the heat at the equator, which makes the air rise and travel north and south high in the atmosphere, until it subsides again in the horse latitudes. The doldrums are also noted for calm periods when the winds disappear altogether.
6. Horse Latitude – Horse latitudes or subtropical highs are subtropical latitudes between 30 and 35 degrees both north and south over the oceans. This region, under a ridge of high pressure called the subtropical high, is an area which receives little precipitation and has variable winds mixed with calm. The belt in the Northern Hemisphere is known as “calms of Cancer” and in the Southern Hemisphere as “calms of Capricorn”.
7. Periodic winds – The winds which change their direction periodically with change in season are called periodic winds. For example, Monsoon.
Monsoon – The word ‘monsoon’ comes from the Arabic word ‘mausim’ which means season. Monsoons are large-scale sea breezes which occur when the temperature on land is significantly warmer or cooler than the temperature of the ocean. These temperature imbalances happen because oceans and land absorb heat in different ways. The monsoon winds change or reverse their direction according to the seasons. The onshore winds bring moisture and heavy rainfall while the offshore winds are relatively dry. The monsoon are mainly associated with South-east Asia and India.
8. Local winds – Local differences in temperature and pressure on the land causes changes in air pressure due to which local wind blows. They are limited to small areas and are known by local names in that area. For example, Chinook, Harmattan, Loo, Mistral, Foehn, etc.
Types of Local Winds
|Name of the local wind||Details|
|Bora||It is a strong, cold, dry north east wind blowing outwards from Hungary to the north of Italy in the upper Adriatic sea.|
|Blizzard||It is a storm or wind which contains large amounts of snow and blows in Tundra region.|
|Brickfielder||It is a hot and dry wind in the desert of Southern Australia that occurs in the summer season.|
|Chinook||It is a warm dry wind which blows down the east side of the Rocky Mountains at the end of winter.|
|Foehn||It is a a hot southerly wind on the northern slopes of the Alps.|
|Harmattan||It is a very hot and dry, dusty easterly or north-easterly wind on the West African coast, occurring from December to February|
|Khamsin||It is a hot and dry southerly or south-easterly wind blowing in Egypt in spring.|
|Levanter||It is a strong easterly wind that blows from the Mediterranean region, through the straits of Gibraltar to the Atlantic.|
|Mistral||It is a strong cold north-westerly wind that blows through the Rh么ne valley and southern France towards the Mediterranean, mainly in winter.|
|Norwester||It is hot dry wind in New Zealand.|
|Purga||It is a a violent cold wind in Russian tundra region.|
|Punas||It is a cold and dry wind blowing in the Andes.|
|Sirocco||It is a hot wind, often dusty or rainy, blowing from North Africa across the Mediterranean to southern Europe.|
|Solano||It is a hot, oppressive wind which blows in the Mediterranean, particularly on the eastern coast of Spain.|
|Santa Ana||It is a strong hot dry wind that blows in winter from the deserts of southern California toward the Pacific Coast.|