# RBSE Class 11 Indian Geography Notes Chapter 7 Monsoon System of India

Go through these RBSE Class 11 Indian Geography Notes Chapter 7 Monsoon System of India contain important concepts so that students can score better marks in the exam.

## Rajasthan Board RBSE Class 11 Indian Geography Notes Chapter 7 Monsoon System of India

Monsoon of India

• Indian climate is called Monsoon climate.
• Indian economy depends on monsoon. That is why, its proper study and forecasting is essential.

Monsoon Concept

• The word Monsoon has originated from the Arabian word ‘Mausim’, which means season.
• Monsoon are the seasonal winds which blow from land to sea for six months and from sea to land for another six months.
• Indian climate is always affected by the monsoon because monsoon winds blow throughout the year.
• Monsoon affects Indian agriculture, industries and other economic activities, so Indian economy is called the Gamble of Monsoon.

Hypothesis of Monsoon

• The main hypothesis of monsoon include Classical Hypothesis, Inter-Tropical Convergence Hypothesis, Cyclonic Hypothesis of Spate, Jet Stream Hypothesis, El-Nino and La-Nina hypothesis.
• The classical hypothesis is related to the distribution of land and water and the thermal conditions.
• The origin of summer monsoon and winter monsoon is due to opposite nature of heat, trap and heat release.

Inter-Tropical Convergence Hypothesis

• This theory was propounded by the German meteorologist H. Flohn.
• The meeting place of south-west trade winds in the southern hemisphere and north-east trade winds in the northern hemisphere is known as the inter tropical convergence zone.
• The origin of monsoon is considered to be the result of conjunction of these two different winds.
• H. Flohn says that monsoon is simply the result of an unusually great northward displacement of the Northern Inter-Tropical Convergence Zone (NITCZ).

Cyclonic Hypothesis of Spate

• According to this theory, monsoon is the result of origin of cyclones.
• The origin of different cyclones is due to the inter tropical fronts formed by the conjunction of different winds.
• The amount of rainfall depends on the intensity of formation of these intertropical fronts.

Jet Stream Hypothesis

• According to this theory, high level wind circulation in the troposphere plays an important role in the origin of monsoon.
• Jet stream is the effected part of high level wind circulation over Himalayas and Tibet region.
• Due to the presence of Tibetan Plateau, one of the branch of jet stream flows in its north and another in its south.
• Jet-stream winds always flow from west to east.
• With the displacement of atmospheric pressure belt, jet stream flow is also displaced towards north and south respectively.

El-Nino and La-Nina Hypothesis

• El Nino is a narrow warm current which appears at the coast of Peru in December.
• When near the coast of Peru, higher temperature than normal is found, it is called El Nino effect and when lesser temperature than normal is found, it is called La-Nina effect.
• The thermal conditions found near the coast of Peru is the main factor deciding the pattern of Indian monsoon.
• This process is given the name ‘Christ Child’ due to its development near Christmas.
• On the development of the conditions of El-Nino, monsoon in India is weaker, and on the development of the conditions of La-Nina, monsoon in India is stronger.

Mechanics of El-Nino effect

• When low air pressure conditions rise in the coast of Peru, the force that pushes out trade winds becomes weaker and hence the force attracting the trade winds gets activated.
• Therefore, the flow of trade winds towards Asia gets weaker and the summer monsoon gets delayed in India.

Mechanism of La-Nina effect

• When the higher air pressure conditions rise in the coast of Peru, the force that pushes out the trade winds becomes stronger and hence the force attracting the trade winds gets deactivated.
• Under the La-Nina condition, the flow of monsoon gets stronger and hence a possibility of early monsoon takes place.

### Monsoon System of India Notes Important Terms

→ Climate: The composite or generally prevailing weather conditions of a region, such as temperature, air pressure, humidity, precipitation, sunshine, cloudiness and winds throughout the year for or a long period of time.

→ Monsoon: The seasonal wind of the Indian Ocean and Southern Asia, blowing from the south-west in summer and from the north-east in winter.

→ Economy: The state of a country or region in terms of the production and consumption of goods and services and the supply of money.

→ Season: A season is a period of the year that is distinguished by specific climatic conditions.

→ Agriculture: The science, art or occupation concerned with cultivating land, raising crops, and feeding, breeding and raising livestock.

→ Industry: Economic activity concerned with the processing of raw materials and manufacturing of goods in factories.

→ Atmospheric pressure: Atmospheric pressure is the pressure exerted by all the layers of the atmosphere on a regional unit on the earth’s surface.

→ Equator: An imaginary line drawn on the earth equidistant from the poles, dividing the earth into the northern and southern hemispheres and constituting the parallel of 0° latitude.

→ Trade Winds: Winds blowing steadily from the sub-tropical high pressure belt to the equatorial low pressure belt in the northern and southern hemispheres are called trade winds.

→ Front: The surface or boundary line bend over the earth’s surface with the help of which two air-masses of the opposite nature meet.

→ Cyclones: A system of winds rotating inwards to an area of low barometric pressure, with an anticlockwise (Northern Hemisphere) or clockwise (Southern Hemisphere) circulation.

→ Sub-tropical Zone: Region found in the upper parts of the tropical zone.

→ Anticyclone: A weather system with high barometric pressure at its centre, around which air slowly circulates in a clockwise or an anticlockwise direction.

→ Inter-tropical convergence zone: A narrow zone near the equator where northern and southern air masses converge, typically producing low atmospheric pressure.

→ Air masses: A body of air with horizontally uniform levels of temperature, humidity and pressure.

→ Jet-Stream: A narrow variable band of very strong predominantly westerly air currents encircling the globe several miles above the earth.

→ Troposphere: The lowest layer of the atmosphere, extending from the earth’s surface to an average height of about 12 kms.

→ Tropic of Capricorn: The parallel of latitude that is approximately 23$$\frac{1}{2}$$° south of the equator and that is the southern-most latitude reached by the overhead sun.

→ Plateau: A land area having a relatively leveled surface considerably raised above adjoining land on at least one side, and often cut by deep canyons.

→ Latitude: The angular distance of a place north or south of the earth’s equator, or of the equator of a celestial object, usually expressed in degrees and minutes.

→ Tropic of Cancer: The parallel of latitude that is approximately 23$$\frac{1}{2}$$° north of the equator and that is the northern-most latitude reached by the overhead sun.

→ El-Nino: An irregularly occurring and complex series of climatic changes affecting the equatorial pacific region, and beyond every few years, characterised by the appearance of unusually warm, nutrient-poor weather of northern Peru and Equator, typically in late December.

→ La-Nina: A cooling of the water in the equatorial pacific, which occurs at irregular intervals, and is associated with widespread changes in weather pattern complementary to those of El Nino, but less extensive and damaging in their effects.

→ Convergence: A location where air flows or ocean currents meet characteristically marked by up-welling (of air) or down-welling (of water).