Lecture 3 Winds (English)

 

Definition: - "The wind that flows parallel to the earth with horizontal speed is given the noun of pure." Or "Wind is such a moving air, whose direction is necessarily parallel to the earth's plane".

Ø There are two types of motion in the atmosphere, vertical and horizontal.

Ø When the air moves from the ground to the top or from the top to the bottom, then this movement is called air wave. Normally we are not able to feel this speed. The origin of clouds, rain, etc. are the result of vertical movement.

Ø When there is horizontal movement of air parallel to the earth, it is called wind.

Ø Winds are named according to the direction in which they blow, such as if the wind is coming from the east, then it is called east and if it is coming from west, then it is called westerly wind.

v Types of Winds

1. Trade Winds: - Due to continuous high temperature at the equator, the air there rises upwards. Thus, a low air pressure area is formed here between 5˚ N to 5˚ S latitudes. Which is called doldrum or calm belt. The winds rising from these regions create high pressure at 35˚ N to 35˚ S latitudes. In the northern hemisphere, the direction of these winds is from north-east to south-west and in the southern hemisphere, the direction of these winds is from south-east to north-west. Due to the movement of these winds in the regular direction, in ancient times, traders used to have a lot of convenience in the operation of ships, that is why they are called trade winds.

2.  West winds: - The area of these winds located between 60˚ – 65˚ latitudes in both the hemispheres is called the sub-polar low pressure belt. In this region, the air flows from the subtropical high-pressure area to the subpolar low-pressure area. The direction of their flow is just opposite to the direction of flow of trade winds. The westerly winds near 40˚ S latitude are called Garjata Chalisa, near 50˚ S latitude - Prachand Pachasa, near 60˚ S latitude - Cheekta Sakh.

3.  East Winds: - Due to the extreme cold in the polar regions and near the poles, the air pressure is very high, as a result of which the air flows from the polar high-pressure area to the subpolar low-pressure area. These winds blow from the north-east in the northern hemisphere and from the south-east in the southern hemisphere. That is why they are also called polar easterly winds.

4.  Local winds: -

A. Land and sea breezes: -

F The mutual exchange of air between the sea and the coastal land due to unequal temperature and refrigeration is called land and sea breeze.

F During the day, the coastal area gets heated much faster than the sea water, thus low air pressure is created on the coastal area, due to which the wind blows from the high-pressure side of the sea towards the land, which is called sea breeze.

F In the night, the land part cools faster than the sea, as a result of which high air pressure is formed on the land, then the wind starts flowing from the land to the sea, which is called land breeze.

B. Mountain and Valley Breeze: -

F These winds also flow between the mountain and the valley as a result of sky temperature and refrigeration.

F Atmospheric pressure is less on the hilly parts during the day and due to sunlight not reaching directly in the valley, the atmospheric pressure is high, then the wind flows from the bottom of the valley towards the mountain. known as anabatic breeze).

F During the night, the air pressure in the mountainous region becomes high and the air pressure in the valley decreases, then the wind starts flowing from the mountain to the valley, these winds are known as mountain breeze / night breeze / katabatic breeze.

5. Monsoon Winds: -

F The exchange of winds between land and oceans due to the temperature and cooling of the continents and oceans is called monsoon winds.

F Monsoon is an Arabic word meaning season. Monsoon is called “Pawas” in Hindi and monsoon winds are called “Pawasi Winds”. Traditionally, monsoon winds are those winds which blow only in a particular season.

F  In summer, the land becomes hotter than the sea, as a result of which low air pressure is formed on the land, then the air flows from the sea to the land.

F In winter, the land cools down faster than the sea, due to which high pressure is generated on the land, as a result of which the air starts flowing from the land towards the sea.

v Two types of monsoon winds blow in the Indian subcontinent –

1. South-west monsoon winds

2. North-East monsoon Winds

v South-west monsoon winds

F The Indian subcontinent is located in the region of north-east trade winds, which blow throughout the year, but low pressure remains in the region of the Ganga River and northern India, due to which the south-west winds are more dominant.

F From April to September, a low-pressure center is formed in the north-west. Then the south-west trade winds from the Indian Ocean start flowing towards the equator, which due to the Caryopsis effect turns towards the low-pressure area on the right side in India.

F These moisture-laden winds rise towards the Asian mountains, start cooling and due to the action of condensation of water vapor present in them, liquefy and start raining.

v North-East monsoon winds

F These winds remain active from October to November. During this, a high-pressure area is formed in the East Asian region, as a result of which the winds start blowing from the north-east, these winds come from the land, that is why there is almost no rain in India due to being dry and moisture-free.

6. Cyclone and Anticyclone

1. Cyclone: -

Ø This is a type of atmospheric disturbance under which a low air pressure center is formed at a particular place, then the direction of wind flow becomes towards the center.

Ø Closed isobars expand around this center. In this way, the air pressure goes from the center to the outside, as a result, air starts blowing from the periphery towards the center.

Ø Whose direction is anticlockwise in the northern hemisphere and clockwise in the southern hemisphere. Thus, this system of near isobars with low pressure in the center is called a cyclone.

Ø Their shape is usually in circular, oval or V shape.

Ø Cyclones have a huge impact on climate and weather. When their speed becomes excessive, they are called Gale.

2.  Anticyclone

Ø They have conditions and characteristics opposite to those of cyclones.

Ø In these, high pressure is created in the center due to which winds start blowing in all the four directions outside.

Ø It is such an air circulation system in which there are isobars and high pressure at the center. The direction of the anticyclone is clockwise in the northern hemisphere and anticlockwise in the southern hemisphere.