Types of wind
1. Planetary Winds:
The winds blowing throughout the year from one latitude to another in response to
latitudinal differences in air pressure are called “planetary or prevailing winds”. They
involve large areas of the globe.
Two most important prevailing winds are trade winds and westerly winds.
2. Trade Winds:
These are extremely steady winds blowing from sub-tropical high pressure areas
(30°N and S) towards the equatorial low pressure belt. These winds should have
blown from the north to south in Northern Hemisphere and south to north in Southern
Hemisphere, but, they get deflected to the right in Northern Hemisphere and to the left
in Southern Hemisphere due to Coriolis effect and Ferrel‟s law. Thus, they blow as
north eastern trades in Northern Hemisphere and south eastern trades in Southern
Hemisphere.
They are also known as tropical easterlies, and they blow steadily in the same
direction. They are noted for consistency in both force and direction.
3. The Westerlies:
These winds blow from sub tropical high pressure belts towards sub-polar low
pressure belts. The westerlies of Southern Hemi sphere are more stronger and constant
in direction than Northern Hemisphere. These winds develop between 40° and 65°S
latitudes and these latitudes are known as Roaring Forties, Furious Fifties and Shriek-
ing Sixties.
4. Periodic Winds:
Periodic winds change their direction periodically with the change in season, e.g.,
Monsoons, Land and Sea Breezes, Mountain and Valley Breezes.
a. Monsoon Winds: These winds are seasonal winds and refer to wind systems that
have a pronounced, seasonal reversal of direction. According to „Flohn‟, monsoon is a
seasonal modification of general Planetary Wind System.
Summer monsoon is called South Westerly Wind and is characterized by highly
variable weather with frequent spells of drought and heavy rains. The winter monsoon
is a gentle drift of air in which winds blow from the north-east and is known as North
Easterly Wind.
b. Land Breeze:
At night, land masses cool quicker than sea due to rapid radiation which results in
high pressure over land and low pressure over sea. And in calm, cloudless weather, air
blows from land to sea. This breeze carries no moisture and is little warm and dry.
c. Sea Breeze:
In day time, the land being hotter than the sea develops low air pressure and the sea
being cool develops high pressure. The air over land rises and is replaced by a cool
breeze known as Sea Breeze from the sea, carrying some moisture.
d. Mountain and Valley Breezes:
A diurnal wind occurs in mountainous regions which are similar to Land and Sea
Breezes. During the day the slopes of mountains are hot and air from valley flows up
the slopes. This is known as “Valley Breeze”. After sunset the pattern is reversed and
cold air slides from mountain to valley and is called “mountain breeze”.
5. Local Winds:
The local difference in temperature and pressure causes local winds. It is of four
types: hot, cold, convectional and slope.
Dr. Tariq M Usmani
Associate Professor
Department of Geography
AMU Aligarh
