Question

Example of seasonal winds

Answer 1

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 Hemi­sphere 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 Shriek­ing 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.

Answer 2

There are different types of wind which flow in specific direction and at a specific time of the year to control the climatic conditions of a large geographical area,and these winds are known as the seasonal winds.

For example:

A seasonal wind which is known as the "monsoon" manipulates the climatic conditions of the Southern Asia including India.