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Types of Winds: Permanent, Secondary &

Local Winds
Home > Geography > Climatology > Types of Winds: Permanent, Secondary & Local Winds

Last Updated: January 1, 2016 by PMF IAS — 4 Comments

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Factors Affecting Wind movement | Co… Temperature Inversion: Types & Effect…

Table of Contents  50% OFF on ALL  Geography GS PDF

1) General
 Environment PDF  Major Crops PDF
circulation of the
atmosphere  Sci & Tech CA PDF  Art & Culture 
1.1) Hadley Cell
1.2) Ferrel Cell
1.3) Polar Cell
1.4) Walker Cell
2) Classification of
Winds
3) Primary Winds or
Prevailing Winds or
Permanent Winds or
Planetary Winds
 3.1) Trade Winds
3.2) Westerlies
3.3) Polar
easterlies
4) Secondary Winds
or Periodic Winds

4.1) Monsoons
4.2) Land Breeze
and Sea Breeze
4.3) Valley
Breeze and
Mountain Breeze
5) Tertiary Winds or
Local Winds

5.1) Loo
5.2) Foehn or
Fohn
5.3) Chinook
5.4) Mistral
5.5) Sirocco
6) Questions

General circulation of the atmosphere

The pattern of planetary winds depend on:
latitudinal variation of atmospheric heating;
emergence of pressure belts;
the migration of belts following apparent path of the sun;
the distribution of continents and oceans;
the rotation of earth.
 The pattern of the movement of the planetary winds is called the
general circulation of the atmosphere. The general circulation of the
atmosphere also sets in motion the ocean water circulation which
influences the earth’s climate.

Hadley Cell
The air at the Inter Tropical Convergence Zone (ITCZ) rises because of
the convection currents caused by low pressure. Low pressure in turn
occurs due to high insolation. The winds from the tropics converge at
this low pressure zone.
The converged air rises along with the convective cell. It reaches the
top of the troposphere up to an altitude of 14 km, and moves towards
the poles. This causes accumulation of air at about 30° N and S. Part of
the accumulated air sinks to the ground and forms a subtropical high.
Another reason for sinking is the cooling of air when it reaches 30° N
and S latitudes.
 Down below near the land surface the air flows towards the equator as
the easterlies. The easterlies from either side of the equator converge
in the Inter Tropical Convergence Zone (ITCZ). Such circulations from
the surface upwards and vice-versa are called cells. Such a cell in the
tropics is called Hadley Cell.

Ferrel Cell
In the middle latitudes the circulation is that of sinking cold air that
comes from the poles and the rising warm air that blows from the
subtropical high. At the surface these winds are called westerlies and
the cell is known as the Ferrel cell.

Polar Cell
At polar latitudes the cold dense air subsides near the poles and blows
towards middle latitudes as the polar easterlies. This cell is called the
polar cell.
These three cells set the pattern for the general circulation of the
atmosphere. The transfer of heat energy from lower latitudes to higher
latitudes maintains the general circulation.
The general circulation of the atmosphere also affects the oceans. The
large-scale winds of the atmosphere initiate large and slow moving
currents of the ocean. Oceans in turn provide input of energy and water
vapour into the air. These interactions take place rather slowly over a
large part of the ocean.

Walker Cell
Warming and cooling of the Pacific Ocean is most important in terms of
general atmospheric circulation.
The warm water of the central Pacific Ocean slowly drifts towards
South American coast and replaces the cool Peruvian current. Such
 appearance of warm water off the coast of Peru is known as the El
Nino.
The El Nino event is closely associated with the pressure changes in
the Central Pacific and Australia. This change in pressure condition
over Pacific is known as the southern oscillation.
The combined phenomenon of southern oscillation and El Nino is
known as ENSO.
In the years when the ENSO is strong, large-scale variations in weather
occur over the world. The arid west coast of South America receives
heavy rainfall, drought occurs in Australia and sometimes in India and
floods in China. This phenomenon is closely monitored and is used for
long range forecasting in major parts of the world. (El-Nino in detail
later)

Classification of Winds
Permanent winds or Primary winds or Prevailing winds or Planetary Winds

The trade winds, westerlies and easterlies.

Secondary or Periodic Winds

Seasonal winds: These winds change their direction in different

seasons. For example monsoons in India.
 Periodic winds: Land and sea breeze, mountain and valley breeze.

Local winds

These blow only during a particular period of the day or year in a small
area.
Winds like Loo, Mistral, Foehn, Bora.

Primary Winds or Prevailing Winds or

Permanent Winds or Planetary Winds
These are the planetary winds which blow extensively over continents
and oceans.
The two most well- understood and significant winds for climate and
human activities are trade winds and westerly winds.

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Trade Winds
The trade winds are those blowing from the sub-tropical high pressure
areas towards the equatorial low pressure belt.
Therefore, these are confined to a region between 30°N and 30°S
throughout the earth’s surface.
 They flow as the north-eastern trades in the northern hemisphere and
the south-eastern trades in the southern hemisphere.
This deflection in their ideally expected north-south direction is
explained on the basis of Coriolis force and Farrel’s law.
Trade winds are descending and stable in areas of their origin (sub-
tropical high pressure belt), and as they reach the equator, they become
humid and warmer after picking up moisture on their way.
The trade winds from two hemispheres meet at the equator, and due to
convergence they rise and cause heavy rainfall.
The eastern parts of the trade winds associated with the cool ocean
currents are drier and more stable than the western parts of the ocean.

Westerlies
The westerlies are the winds blowing from the sub-tropical high
pressure belts towards the sub polar low pressure belts.
They blow from southwest to north-east in the northern hemisphere
and north-west to south-east in the southern hemisphere.
The westerlies of the southern hemisphere are stronger and persistent
due to the vast expanse of water, while those of the northern
hemisphere are irregular because of uneven relief of vast land-masses.
The westerlies are best developed between 40° and 65°S latitudes.
These latitudes are often called Roaring Forties, Furious Fifties, and
Shrieking Sixties – dreaded terms for sailors.
The poleward boundary of the westerlies is highly fluctuating. There are
many seasonal and short-term fluctuations. These winds produce wet
spells and variability in weather.

Polar easterlies
The Polar easterlies are dry, cold prevailing winds blowing from north-
east to south-west direction in Northern Hemisphere and south-east to
north-west in Southern Hemisphere.
 They blow from the polar high-pressure areas of the sub-polar lows.

Secondary Winds or Periodic Winds

These winds change their direction with change in season.
Monsoons are the best example of large-scale modification of the
planetary wind system.
Other examples of periodic winds include land and sea breeze,
mountain and valley breeze, cyclones and anticyclones, and air masses.

Monsoons
Monsoons were traditionally explained as land and sea breezes on a
large scale. Thus, they were considered a convectional circulation on a
giant scale.
The monsoons are characterized by seasonal reversal of wind
direction.
During summer, the trade winds of southern hemisphere are pulled
northwards by an apparent northward movement of the sun and by an
intense low pressure core in the north-west of the Indian subcontinent.
While crossing the equator, these winds get deflected to their right
under the effect of Coriolis force.
These winds now approach the Asian landmass as south-west
monsoons. Since they travel a long distance over a vast expanse of
water, by the time they reach the south-western coast of India, they are
over-saturated with moisture and cause heavy rainfall in India and
neighboring countries.
During winter, these conditions are reversed and a high pressure core is
created to the north of the Indian subcontinent. Divergent winds are
produced by this anticyclonic movement which travels southwards
towards the equator. This movement is enhanced by the apparent
southward movement of the sun. These are north-east or winter
 monsoons which are responsible for some precipitation along the east
coast of India.
The monsoon winds flow over India, Pakistan, Bangladesh, Myanmar
(Burma), Sri Lanka, the Arabian Sea, Bay of Bengal, southeastern Asia,
northern Australia, China and
Outside India, in the eastern Asiatic countries, such as China and
Japan, the winter monsoon is stronger than the summer monsoon. (we
will study about monsoons in detail while studying Indian Climate)

Land Breeze and Sea Breeze

The land and sea absorb and transfer heat differently. During the day
the land heats up faster and becomes warmer than the sea. Therefore,
over the land the air rises giving rise to a low pressure area, whereas
the sea is relatively cool and the pressure over sea is relatively high.
Thus, pressure gradient from sea to land is created and the wind blows
from the sea to the land as the sea breeze. In the night the reversal of
condition takes place. The land loses heat faster and is cooler than the
sea. The pressure gradient is from the land to the sea and hence land
breeze results.
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Valley Breeze and Mountain Breeze

In mountainous regions, during the day the slopes get heated up and air
moves upslope and to fill the resulting gap the air from the valley blows
up the valley. This wind is known as the valley breeze. During the night
the slopes get cooled and the dense air descends into the valley as the
mountain wind. The cool air, of the high plateaus and ice fields draining
into the valley is called katabatic wind.
 Another type of warm wind (katabatic wind) occurs on the leeward side
of the mountain ranges. The moisture in these winds, while crossing
the mountain ranges condense and precipitate. When it descends down
the leeward side of the slope the dry air gets warmed up by adiabatic
process. This dry air may melt the snow in a short time.

Tertiary Winds or Local Winds

Local differences of temperature and pressure produce local winds.
Such winds are local in extent and are confined to the lowest levels of
the troposphere. Some examples of local winds are discussed below.
Loo
Harmful Wind
In the plains of northern India and Pakistan, sometimes a very hot and
dry wind blows from the west in the months of May and June, usually in
the afternoons. It is known as Its temperature invariably ranges
between 45°C and 50°C. It may cause sunstroke to people.

Foehn or Fohn
Beneficial Wind
 Foehn is a hot wind of local importance in the Alps. It is a strong, gusty,
dry and warm wind which develops on the leeward side of a mountain
range. As the windward side takes away whatever moisture there is in
the incoming wind in the form of orographic precipitation, the air that
descends on the leeward side is dry and warm (Katabatic Wind).
The temperature of the wind varies between 15°C and 20°C. The wind
helps animal grazing by melting snow and aids the ripening of grapes.

Chinook
Beneficial Wind
Foehn like winds in USA and Canada move down the west slopes of the
Rockies and are known as
It is beneficial to ranchers east of the Rockies as it keeps the
grasslands clear of snow during much of the winter.

Mistral
Harmful Wind
Mistral is one of the local names given to such winds that blow from
the Alps over France towards the Mediterranean Sea.
It is channeled through the Rhine valley. It is very cold and dry with a
high speed.
It brings blizzards into southern France.

Sirocco
Harmful Wind
Sirocco is a Mediterranean wind that comes from the Sahara and
reaches hurricane speeds in North Africa and Southern Europe.
It arises from a warm, dry, tropical air mass that is pulled northward by
low-pressure cells moving eastward across the Mediterranean Sea, with
the wind originating in the Arabian or Sahara deserts. The hotter, drier
 continental air mixes with the cooler, wetter air of the maritime cyclone,
and the counter-clockwise circulation of the low propels the mixed air
across the southern coasts of Europe.
The Sirocco causes dusty dry conditions along the northern coast of
Africa, storms in the Mediterranean Sea, and cool wet weather in
Europe.

Questions
Multiple choice questions

1. Multiple choice questions. (i) If the surface air pressure is 1,000 mb, the
air pressure at 1 km above the surface will be: (a) 700 mb (c) 900 mb
(b) 1,100 mb (d) 1,300 mb
2. The Inter Tropical Convergence Zone normally occurs: (a) near the
Equator (b) near the Tropic of Cancer (c) near the Tropic of Capricorn
(d) near the Arctic Circle
3. The direction of wind around a low pressure in northern hemisphere is:
(a) clockwise (c) anti-clock wise (b) perpendicular to isobars (d) parallel
to isobars
4. Which one of the following is the source region for the formation of air
masses? (a) the Equatorial forest (c) the Siberian Plain (b) the
Himalayas (d) the Deccan Plateau

30 words

1. While the pressure gradient force is from north to south, i.e. from the
subtropical high pressure to the equator in the northern hemisphere,
why are the winds north easterlies in the tropics.
2. What are the geostrophic winds?
3. Explain the land and sea breezes.

150 words

Discuss the factors affecting the speed and direction of wind.

 Draw a simplified diagram to show the general circulation of the
atmosphere over the globe. What are the possible reasons for the
formation of subtropical high pressure over 30° N and S latitudes?
Why does tropical cyclone originate over the seas? In which part of the
tropical cyclone do torrential rains and high velocity winds blow and
why?

Primary References: NCERT Geography, Spectrum’s Geography [Amazon and

Flipkart], Certificate Physical and Human Geography [Amazon and
Flipkart], and Savindra Singh [Amazon and Flipkart]