Climate Class 9 Notes: CBSE | Chapter 4 | Geography
Introduction:- In Climate class 9 notes we read about Climate, India climate, Jet Stream, distribution of Rainfall, Indian Monsoon and so many other topics we read in this notes. So let’s start it.
What is Climate?
- It refers to the sum total of weather conditions and variation over a large area for a long period of time(more than 30years).
- Climate is the average weather in a given area over a longer period of time.
- A description of a climate includes information on, e.g. the average temperature in different seasons, rainfall, and sunshine.
What is Weather?
- It refers to the state of the atmosphere over an area at any point in time.
- Weather is different in different parts of the world and changes over minutes, hours, days, and weeks.
- The element of weather and climate:-
- 1. Temperature,
- 2. Atmospheric pressure,
- 3. Wind,
- 4. Humidity,
- 5. Precipitation.
What is Monsoon?
- It refers to a seasonal reversal in the wind direction during a year.
- The word derived from the Arabic word ‘MAUSIM’ which means season.
- The climate of India is described as a monsoon type climate.
- The factor of climate control:-
- Latitude ➢ Due to the curvature of earth the number of solar energy receives from the equator to the poles decreasing and it affects the climate of a particular region.
- Altitude ➢ As we move from the surface of the earth to a higher place the temperature decreases. For ex-The hills are cooler during summer.
- The pressure and wind system ➢ The winds usually blow from high-pressure areas to a low-pressure area. In high-temperature areas mostly low pressure generates and in winter mostly high-pressure areas generate. These pressure and wind system also affect the climate.
Distance from the sea:- As the distance from the sea increases the influencer of the weather also increases. The areas very near to the sea (coastal area) not more influenced by the weather condition.
Factor affecting India climate:-
- Latitude ➢ The tropic of cancer pass through the middle of the country from Rann of Kuchchh(west) to Mizoram(east). Half of the country lying south of the tropic of cancer. Half of the country lying north of the Tropic of cancer. So India’s climate is tropical as well as subtropical.
- Altitude ➢ India has mountains to the North with an average height of 6000meter. These mountains prevent cold winds from central Asia from entering to the India sub-continent. So our country experiences less winter as composed in central Asia.
- Pressure & wind system ➢ India lies in the region of northeasterly winds. Winds always blow from high-pressure areas to low-pressure areas.
- In summer ➥ A low-pressure area develops over interior Asia and northwestern India. A high-pressure area develops over the southern Indian ocean. The winds blow from south to north and cross the equator. These winds blow over the warm ocean and gather moisture and rainfall over the mainland of India.
- In winter ➥ A high-pressure area develops over the north of Himalayas. A low-pressure area develops over the southern ocean. Cold dry winds blow from north to south.
- Coriolis force ➥ It is a force that caused by earth rotation. This force is responsible for deflecting the direction of winds. In the north the direction of wind toward the right. In the southern hemisphere the direction of wind toward left.
4. Upper air circulation ➢ Upper air circulation is dominated by the westerly flow. An important component of this flow is the jet stream.
Jet Stream ➥
- These streams are located over 27-30degree north latitude.
- They are known as subtropical westerly jet streams.
- In summers, these streams blow the north of Himalayas.
- And in winter season these blow the south of Himalayas.
- These are a narrow belt of high altitude(above 12000m).
- This speed varies from 100km/h in summer and 184km/h in winter.
5. Western cyclonic disturbance ➢
- These are the weather phenomena of the winter month.
- These are westerly flow from the Mediterranean region.
- They influence the weather of north and north-west of India.
- Tropical cyclone occurs during the monsoon as well as in October November is the part of this.
Ocean current:- Ocean current also affects the climate of a particular region. If the oceans current are hit the atmosphere is also cool, if ocean current is hot the atmosphere is hot.
Explain Indian Monsoon
- The climate of India is a monsoon type.
- The monsoon is experienced in the tropical area roughly between 20N & the 20S.
- To understand the mechanism of the monsoon the following fact are important ➥
- The difference in heating and cooling of land and water.
- The shift of the position of the Intertropical Convergence Zone(ITCZ).
- The pressure of high-pressure area cast of Madagascar at the 20S over the Indian’s oceans.
- The Tibetan plateau gets intensely heated during summer.
- The movement of westerly jet streams to the north of the Himalayas.
Explain onset of the Monsoon
- The monsoon arrives from June to September.
- The duration of the monsoon is between 100 to 120days.
- The monsoon arrives at the southern tip of the Indian peninsula by 1st week of June.
- Then it proceeds into two branches:-
➢ Arabian sea branch
➢ Bay of Bengal branch
- Arabian sea branch reaches Mumbai about 10th June.
- The Bay of Bengal branch also advance. It arrives in Assam in the first week of June.
- The lofty mountain deflects the winds towards the Indian subcontinent.
- By mid-June, the Arabic sea branch arrives over Saurashtra-Kachchh and central parts of the country.
- The Arabic and Bay of Bengal branch merge over the northern-western part of Ganga plain.
- Delhi river rainfall by Bay of Bengal branch by the end of 24 June.
- By the 1st July western U.P., Punjab, Haryana & Western Rajasthan experience the monsoon.
- By mid-July, the monsoon reaches Himachal Pradesh and the rest of the country.
Define Withdrawal/offset of the monsoon
- The withdrawal of the monsoon in the northern state of India start by early September.
- By mid-October, it withdraws completely from the northern half of the peninsular.
- By early December the monsoon has withdrawn from the rest of the country.
Arrival and retreating of monsoon in islands
- The island receives rainfall(monsoon) from the last week of April and the first week of May.
- It arrives from north to south.
- It withdraws from north to south from 1st week of December to the first week of January.
- By this time the whole country is in the influence of the winter season.
Explain all about the season(4 seasons):-
- The cold weather season(winter)
- The hot weather season(summer)
- Advancing monsoon(rainy season)
- Retreating monsoon(transition season)
1. The Cold-weather season
- This season begins from mid-November in northern India and stays still February.
- The coldest months are December and January.
- The temperature decreases from south to north.
- The average temperature in Chennai- 24 to 25degree, Northern plain- 10 to 15degree.
- Feature of this season is:-
➢ Days are warm night is cold
➢ Forest are common in the north
➢ Slopes of the Himalayas experience snowfall
➢ Clear sky
➢ Low humidity
➢ The northern trade winds prevail in the country.
➢ They blow from lad to sea hence in must part of the country there is the dry season.
➢ Due to these winds rainfall occurs in Tamil Nadu cost.
- An important feature of winter:-
➢ The northern plain in the influence of western cyclonic disturbance.
➢ This wind blows from the western east.
➢ In the winter season, the rain comes and snowfall called due to it.
➢ The amount of winter rainfall is known as ‘Mahawat’. Mahawat is important for rabi crops.
2. The Hot-weather season
- This begins from March to May.
- This due to the north world movement toward the sun.
- In March, the highest temperature is 38degree and in April- M.P. & Gujarat the temperature is 42degree.
- In May, the Northwest part of India receives a temperature of about 45C.
- An important feature of the summer season in the ‘Loo’.
- These are strong, dusty, hot, and dry winds, and winds caused damages to poverty.
- These are associated with rain and thunderstorm with hail.
- West Bengal is known as ‘Kal Baisakhi‘.
- These shower help in reopening mango.
3. The Rainy season
- It is time duration mid-June to mid-September.
- A low-pressure area generated over the northern plain.
- A high-pressure area in origination over the south of the Indian ocean.
- The southeast trade winds originate over the southern ocean and cross the equator and blow over Indian peninsular.
- The winds blow over the warm ocean and they bring with them a lot of moisture.
- The speed of winds 150km/h.
- These winds rainfall over Indian peninsular.
- Western ghat receives high rainfall near about 250cm.
- The rains occur in breaks(dry spell of the season this rainless interval).
- Northeast in the area receives more rainfall is known as ‘Massi’.
4. The Transition season
- It time duration is October to November.
- Due to the apparent movement of the sun toward the south.
- The monsoon through became weaker the southeast trade wind also become weak and start withdrawn from the northern plain.
- After this season we experience winter season.
- Feature of this season:-
- Sky is clear
- Days were warm in compare of night
- The land has more moisture
- Day heat is known as ‘October heat’.
- In this season low-pressure area is generated in the Bay of Bengal by early November.
- Due to this the cyclone occurs and made may destruction to the eastern coast.
Define distribution of Rainfall
- Western coast receives rainfall near about 260cm.
- The North-Eastern part receives rainfall of about 400cm.
- Rajasthan, Gujarat, Haryana, Punjab receives rainfall less than 60cm.
- Plateau region receives very low rainfall.
- J&K the rainfall is very low but there the people experience the snowfall.
Monsoon as a unifying bond
- Monsoon work as a unifying bond Himalayas protects the subcontinent from extremely cold winds from Central Asia.
- Due to this, we have a very moderate temperature.
- In the peninsular plateau under the influence of the sea from three sides, it has a moderate temperature.
- Due to the seasonal reversal of winds, we experience the 4season.
- Due to the apparent movement of the sun toward the north word and southward the air pressure area keep changing which influences the wind system.
About- Climate class 9 notes
In Climate class 9 notes we read about the distribution of Rainfall, Transition season, Hot-weather, rainy season and so many other topics we read in Climate class 9 notes. I hope you like Climate class 9 notes And if you like this notes then please give your feedback in the comment box(below).
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