World Geography / Climatology
Classification of winds is done based on both global as well as local phenomena. The movement of air to a low pressure area
from a high pressure area is generally called wind. There are 3 types of winds on earth namely, Planetary, Secondary and Local winds. Winds can
be permanent or temporary in nature. Sometimes, winds will be given the name of the direction from which they blow. For example, the winds
blowing from the East in the polar region are called Polar Easterlies.
Planetary winds are nothing but the Permanent winds.
Permanent winds are also called Global winds or Primary winds or Prevailing winds. These are again classified into 3 different types of winds
namely, Trade winds, Westerlies and Polar Easterlies.
Secondary Winds are also known as Seasonal Winds or Periodic Winds. They are confined to a particular area and to a
particular season. They change their direction with season. These
types of seasonal winds are quite strong in nature.
The best example of seasonal winds or secondary winds is Monsoonal Wind system in
Indian ocean. Other examples of periodic winds are Sea Breeze and Land Breeze, Mountain Breeze and Valley Breeze, etc.
Monsoon Wind System
- During the summer, when the Sun is in Northern hemisphere, an intense low pressure zone is created in the northern region of the
Indian subcontinent. Because of this low pressure zone, the Trade winds of the southern hemisphere are pulled towards the North.
- These Trade winds are deflected to their right while crossing the Equator because of Coriolis force arising due to Earth's rotation. These
winds are responsible for south-west monsoon in Indian subcontinent and the adjacent surrounding areas.
- As they travel over the Indian Ocean for a large distance before they reach the land, they are very much saturated with moisture and induce
heavy rainfall in the Indian subcontinent and the
adjacent neighboring countries.
- During the winter, the weather conditions are exactly reversed. During winter, a high pressure zone is created in the northern
region of the Indian subcontinent and winds start to flow southwards towards the Equator because of the low pressure region that is
created by the southward movement of the Sun. These winds are responsible for north-east monsoon in India.
Sea Breeze and Land Breeze
Sea Breeze and Land Breeze are formed at the coast and formed within a day due to thermal and pressure gradient between sea and land.
Because of higher specific heat, sea cools and heats slowly and because of low specific heat, land cools and heats rapidly.
During the day time, land rapidly heats up and hence temperature increases and pressure decreases and sea heats up slowly and hence
temperature decreases and pressure increases.
During the day winds blow from the sea to the land which are called sea breeze
(cool). During the night, there is reversal in phenomenon and are called land breeze (dry).
Mountain Breeze and Valley Breeze
In mountainous region, there is Mountain Breeze Valley Breeze phenomenon very much similar to Sea Breeze Land Breeze.
day time, the valleys will be hot when compared to the mountains and hence air flows up the slopes from the valley towards the mountains
which is called Valley Breeze. During the nights, the phenomenon is reversed and cool air slides down from mountain peaks to
valleys which is called Mountain Breeze.
Tertiary or Local Winds
Local winds cover only small areas at a local level. There are different types of local or tertiary winds formed due to local changes in
temperature and pressure caused by the immediate influence of surrounding terrains.
Different Types of Local Winds
- Blizzards - Blizzard winds blow from North Pole to North Canada. These are strong cold chilly winds occurring during winter. They
bring snow storms and life comes to standstill because of these winds. Sometimes, Blizzard winds reach Central US plains where they are called
- Chinooks - Along the slopes of Rocky Mountains, strong warm winds blow down in Western US known as Chinook winds or Snow Eaters
(which melt snow) during winter. These are crucial for ranching in Western US. Pastures are exposed because of Chinook winds and become suitable
- Santa Ana - Santa Ana winds are strong hot dry and dust laden winds in summer near Mojave desert or Mexican desert. In Death valley, high
temperature is due to Santa Ana winds.
- Etesian or Meltemi - These are dry and strong northern winds that emanate from north Aegean Sea during the summer and having its
effect felt in Greece, Turkey and the surrounding areas. These winds are generally strong in the afternoons and calm down in the evenings.
- In the continent of South America, the names of different local winds are Zonda winds in Chile and Pampero winds in Argentina,
Paraguay and Uruguay.
- There exists different types of local winds in Mediterranean region. From Morocco, Algeria and Tunisia hot and dry winds flow towards
Mediterranean sea called Sirocco.
From Alps to Mediterranean sea, strong cold winds in winter called Mistral winds pass
through Rhine Valley region. Citrus orchids are destroyed by these winds.
- Khamsin winds blow from Egypt to Red Sea. Ghibli winds blow in Libya, Chad and Mauritania.
- From Sahara desert to Gulf of Guinea, winds called Harmattan, blow in summer hot. They are dry dust carrying storms. They bring small
showers, which bring down the temperature temporarily and people will have relief, hence they are sometimes called Doctor Harmattan.
- In Siberia in winter, strong winds called Burans blow out in different directions due to strong high pressure zone. These winds
cannot reach India because of Himalayas. When Buran winds reach China, Japan and Korea, the temperature will be below 00C. When they
move to Iran also, the temperature is below 00C.
- Fohn or Foehn is a local wind of Switzerland, Austria and Alps of Germany. These are strong and cold winds that blow in winter.
- In Arabian desert, the winds that blow are Simoon winds.
- In India, from March to May, there is strong convective winds blow during summer afternoons. Winds blow from West to East. Sometimes, they
carry dust storms and drizzles.
They are called Loo in Punjab and Haryana. Andhi in Uttar Pradesh and Kal Baisakhi
in Bihar and West Bengal. Exposure to these winds is harmful and may result in sunstroke.
- In Deccan Plateau region of India, there will be Mango Showers in summer afternoons which are useful for increase in mango
These types of winds are sometimes misconstrued as Secondary winds because they are often called pre-Monsoon showers but
strictly speaking they are not at all related to Monsoon but one of the types of local winds in India.
- In South-Eastern Australia, Southerly Buster winds blow from New Zealand and Tasmania to Australia.