Chapter 4 Climate NCERT Solutions for Class 9 Geography

NCERT Solutions Class 9 Geography Chapter – Climate: The climate of India is monsoon type and various factors are responsible for onset and advancement of monsoon in India. Solutions of the chapter ‘Climate’ Class 9 are given below.

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NCERT Solutions for Class 9 Social Science Geography Chapter 4 Climate


Intext Questions:

Find Out: Page No: 27

1. Find out why the houses in Rajasthan have thick walls and flat roofs.

Answer

The thick walls of the houses insulate the people against the heat in summer and extreme cold in winter due to the desert. The thick walls do not allow the heat to get into the houses while the flat roofs help rain harvesting by retaining the rain water.

2. Find out why is it that the houses in the Tarai region and in Goa and Mangalore have sloping roofs.

Answer

The Tarai region, Goa and Mangalore receive heavy rains during monsoon seasons thus the houses have sloping roofs so that the rainwater flows off the roof. The flat roofs would retain water that could cause damages to the houses.

3. Why are houses in Assam built on stilts?

Answer

Assam receives abundant rainfall. Houses are built on stilts above the ground to avoid flooding of houses and also to keep houses safe from wild animals.

4. Why most of the world’s deserts are located in the western margins of continents in the subtropics?

Answer

Most of the world’s deserts are located in the western margins of continents in the subtropics because trade winds that blow in the region shed their moisture on the eastern side. They become dry by the time they reach the western margin of the continent.

Cold ocean currents also tend to stabilise the air over the coast and inhibit cloud formation.


Exercises:

Page No: 39

Q.1. Choose the correct answer from the four alternatives given below.

(i) Which one of the following places receives the highest rainfall in the world?
(a) Silchar
(b) Mawsynram
(c) Cherrapunji
(d) Guwahati

Ans:
(b) Mawsynram

(ii) The wind blowing in the northern plains in summers is known as:
(a) Kaal Baisakhi
(b) Loo
(c) Trade Winds
(d) None of the above

Ans:
(b) Loo

(iii) Which one of the following causes rainfall during winters in north-western part of India,
(a) Cyclonic depression
(b) Retreating monsoon
(c) Western disturbances
(d) Southwest monsoon

Ans:
(c) Western disturbances

(iv) Monsoon arrives in India approximately in:
(a) Early May
(b) Early July
(c) Early June
(d) Early August

Ans:
(c) Early June

(v) Which one of the following characterises the cold weather season in India?
(a) Warm days and warm nights
(b) Warm days and cold nights
(c) Cool days and cold nights
(d) Cold days and warm nights

Ans:
(c) Cool days and cold nights

Q.2. Answer the following questions briefly.

(i) What are the factors affecting the climate of India?

Ans:
The factors controlling the climate of India are:

  • Latitude
  • Altitude
  • Pressure and winds (jet streams)
  • Distance from the sea
  • Relief or mountains

(ii) Why does India have a monsoon type of climate?

Ans:
India has a monsoon type of climate because of the strong influence of the monsoon winds over the sub-continent. The summer monsoons cause heavy rainfall when they blow from sea to land. The winter monsoon winds blow from the interior of the continent to the sea and do not cause much rain. There is a seasonal reversal of the wind system ‘monsoon’.

(iii) Which part of India does experience the highest diurnal range of temperature and why?

Ans:
The Thar desert experiences the highest diurnal range of temperature. This is because during the day the temperature rises to over 50°C, and at night due to the absence of the sun and lack vegetation the temperature drops to below 15°C the same night.

(iv) Which winds account for rainfall along the Malabar Coast?

Ans:
Arabian Sea Branch of the South West summer Monsoons.

(v) What are jet streams and how do they affect the climate of India?

Ans:
Jet streams are a narrow belt of high altitude (above 12000 m) westerly winds in the troposphere. The westerly flows are responsible for the western disturbances experienced in the north and north-western parts of the country.

(a) Their speed varies from about 110 km/h in summer to about 184 km/h in winter.

(b) A number of separate jet streams have been identified.

(c) The most constant are the mid latitude and subtropical jet streams.

(d) Jet streams over the Indian peninsula during the summer affect the monsoon.

(e) The subtropical westerly jet stream blow south of the Himalayas and is responsible for the western cyclonic disturbances experienced in the north and north western parts of the country.

(f) An easterly jet stream blows over peninsular India. It affects the coastal regions of the country and is responsible for tropical cyclones during the monsoon as well as during the October to November period.

(g) They have immense importance for the cultivation of Rabi crops in the North India.

(vi) Define monsoons. What do you understand by “break” in monsoon?

Ans:
Monsoon: The word monsoon has been derived from the Arabic word ‘mausim’ which means season.

Monsoon refers to the seasonal reversal in the wind direction during a year. In this season the winds blow from land to sea for 6 months and from sea to land for 6 months.

The break in the monsoon: It refers to the dry spells when the monsoon rain takes place only for a few days at a time. It is characterised by rainless intervals.

These breaks are related to the movement of the monsoon trough. When the axis of the monsoon trough lies over the plains, then the rainfall is heavier there. When the trough moves towards the Himalayas, the plains are dry but there is heavy rainfall occur over the mountains.

(vii) Why is the monsoon considered a unifying bond?

Ans:
The monsoon is considered a unifying bond because:

  • The Indian landscape, its flora and fauna, etc. are highly influenced by the monsoon.
  • These monsoon winds bind the whole country by providing water for agricultural activities.
  • Most of the festivals in India that are related to agricultural cycle may be known by different names in different parts of the country, but their celebration is decided by the monsoon.
  • Year after year, people of India from north to south and from east to west, eagerly await the arrival of the monsoon. The river valleys which carry this water also unite as a single river valley unit.


Q.3. Why does the rainfall decrease from the east to the west in Northern India?

Answer:
The Bay of Bengal branch of south-west monsoon moves towards northeast carrying more moisture and they give heavy rainfall in this region. As they move further towards west, they carry less moisture content with themselves resulting in decrease in rainfall in the west.

Q.4. Give reasons as to why:

(i) Seasonal reversal of wind direction takes place over the Indian subcontinent?

Ans:

  • Seasonal reversal of wind direction over the Indian subcontinent takes place due to temperature and pressure differential causing different pressure conditions over land and seas.
  • In summer the land mass of India is warmer than the surrounding sea and a low-pressure area develops over interior Asia as well as over north-western India. The sea is cooler, thereby having higher pressure. So, the winds blow from sea to land and it is called south-wets monsoon. with winds blowing from southwest to northeast.
  • In winter the land has high pressure while the sea has low pressure. There is a high-pressure area north of the Himalayas. Cold winds blow from this region to the low-pressure areas over the oceans to the south. Therefore, the winds blow towards the sea from northeast to southwest.
  • Thus, a seasonal reversal of wind direction takes place.

(ii) The bulk of rainfall in India is concentrated over a few months.

Ans:
In India the bulk of the rainfall is concentrated over a few months. The main source of rainfall is the monsoon wind which. The duration of the monsoon is between 100-120 days from early June to mid-September. Thus, we can say that rainfall in India is concentrated over a few months.

(iii) The Tamil Nadu coast receives winter rainfall winds.

Ans:
During the winter season the Tamil Nadu coast receives rain from the north east Monsoon which blow from land to sea. During the winter season, the north-west trade winds prevail over the country. They blow from land to sea and hence for most part of the country it is a dry season. Some amount of rainfall occurs on the Tamil Nadu coast from these winds as here they blow from sea to land.

(iv) The delta region of the eastern coast is frequently struck by cyclones.

  • Ans:
    The Bay of Bengal is the centre of various pressure changes and hence there is always a chance of development of cyclone. By early November, the low-pressure conditions over north western India get transferred to the Bay the Bengal. This shift is responsible for the occurrence of cyclonic depressions which originate over the Andaman Sea. These then cross the eastern coast causing heavy widespread rain leading to great damage to life and property.
  • The thickly populated deltas of the Godavari, the Krishna and the Kaveri are frequently struck by cyclones which cause great damage to life and property.
  • Sometimes these cyclones arrive at the coasts of Odisha, West Bengal and Bangladesh.

(v) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone.

Ans:
Relief/Mountains play an important role in the distribution of rainfall in India. The moisture laden winds (South West Monsoons) cause heavy rain on the windward slopes of the Western Ghats and Khasi-Garo hills. As the winds cross over to the leeward slopes, there is less rainfall as most of it has been deposited on the slope facing the winds. All the area on the leeward side is deprived of rain and is drought prone. Rajasthan also lies in the rain shadow of the Aravalli hills.

Q.5. Describe the regional variations in the climatic conditions of India with the help of suitable examples.

Answer:
The great regional variations in the climatic conditions of India are seen mainly in temperature and rainfall.

Temperature: In summer the temperature rises above 50° Cin some parts of Rajasthan while in Jammu and Kashmir it may be around 20 C at the same time. During winter the temperature goes down to even minus 45 C while it may be around 22 c in the Thiruvananthapuram.

Coastal areas have a moderate climate while the interior of India has extreme or continental climate.

Precipitation: The rainfall is as high as 400cm in in Meghalaya while it is less than 10 cm in W. Rajasthan and Ladakh. Most part of India gets rainfall between June to September while Tamil Nadu receives rainfall between November and December.

Q.6. Discuss the mechanism of monsoons.

Answer:
Following are the factors responsible for the mechanism of monsoon:

  • The differential heating and cooling of land and water creates low pressure on the landmass of India while the seas around experience comparatively high pressure.
  • The Inter Tropical Convergence Zone (ITCZ) is normally positioned about 5°N of the equator. It shifts over the Ganga plains during summer. It is also known as the monsoon trough during the monsoon season.
  • The high-pressure area, east of Madagascar is approximately 20°S over the Indian Ocean. This area affects the Indian Monsoon.
  • The Tibetan plateau gets intensely heated during summer. This results in strong vertical air currents and formation of high pressure over the plateau. This high-pressure zone is about 9 km above the sea level.
  • The westerly jet stream moves to the north of the Himalayas, and the tropical easterly jet stream moves over the Indian Peninsula during summer.
  • The periodic change in pressure conditions between Pacific Ocean and the Indian Ocean that is known as the Southern Oscillation or SO also affects the monsoon.
  • The difference in pressure over Tahiti and Darwin is computed to predict the intensity of the monsoons. Tahiti (18°S/149°W) lies in the Pacific Ocean and Darwin (12°30’S/131°E) lies in northern Australia. If the pressure differences are negative, it means a below average and late monsoon

Withdrawal or Retreat of Monsoon The withdrawal or retreat of the monsoon begins in the states of India by early September. By mid-October, it withdraws completely from the northern half of peninsula. By December, the monsoon has withdrawn from the rest of the country.

Q.7. Give an account of weather conditions and characteristics of the cold season.

Answer:
The cold weather season begins from the November in northern India and stays till February. December and January are the coldest months in the northern part of India. The temperature is higher in the south due to the moderating influence of the sea but decreases as one goes northwards where it ranges between 10° and 15° Celsius. Frost is common in the north and there is snowfall in the higher slopes of the Himalayas. Winds blow from land to sea and are dry except when they pick up moisture from the Bay of Bengal and cause rainfall in Tamil Nadu.

(i) The weather is normally marked by clear sky, low temperatures, low humidity and feeble variable winds.

(ii) Days are warm and nights are cold. Frost is common in the north and higher slopes of the Himalayas experience snowfall.

(iii) During this season, the north-east trade winds blow from land to sea and hence for most parts of the country it is a dry season. Some amount of rainfall occurs on the Tamil Nadu coast from these winds as they blow there from sea to land.

(iv) A characteristic feature of the cold weather season over the northern plains is the inflow of cyclonic disturbances from the west and the north-west. The low-pressure systems originate over the Mediterranean Sea and Western Asia and move into India along with the westerly flow. They cause the much-needed winter rains over the plains and snowfall in the mountains.

(v) Although, the total amount of winter rainfall locally known as ‘Mahawat’ is small, it is of immense importance for the cultivation of ‘rabi’ crops.

(vi) The peninsular region does not have a well-defined cold season. There is hardly any noticeable change in temperature pattern during winter due to the moderating influence of the sea.

Q.8. Give the characteristics and effects of the monsoon rainfall in India.

Answer:

Characteristics of the monsoon rainfall in India:

  • The duration of the monsoon varies from 100 to 120 days from early June to mid- September.
  • Around the time of its arrival, the normal rainfall increases suddenly and continues regularly for several days. This is called the ‘burst’ of the monsoon.
  • They are distinguished from the pre-monsoon showers because of their increase in rainfall amount and regularity.
  • The monsoon arrives at the southern tip of the Indian Peninsular generally by the first week of June.
  • The rainfall is unevenly distributed across the country.

Effects of the monsoon rainfall in India:

The monsoon winds bind the whole country by providing water to set the agricultural activities in motion. A good harvest affects the Indian economy favourably.

  • Agriculture in India largely depends on Indian monsoons for water. Late, Low or excessive rains have a negative impact on crops.
  • Due to uneven distribution of rainfall across the country, there are few places that are drought prone and few are flood affected.
  • The monsoon provides India with a diverse climatic pattern. Hence, in spite of the presence of great regional variations, it has a unifying influence upon the country and its people.

For Doing it YourselfPage 40

Q.2. Re-arrange the ten stations in two different sequences

(i) According to their distance from the equator.

(ii) According to their altitude above mean sea-level.

Answer

Maximum/HighestDistance from the EquatorAltitude above Mean Sea Level
LehLeh
DelhiShillong
JodhpurBangalore
ShillongNagpur
KolkataJodhpur
NagpurDelhi
MumbaiThiruvananthapuram
ChennaiMumbai
BangaloreChennai
Minimum / LowestThiruvananthapuramKolkata

Q.3. (i) Name two rainiest stations.

Answer Shillong and Mumbai.

(ii) Name two driest stations.

Answer Leh and Jodhpur.

(iii) Name two stations with most equable climate.

Answer Thiruvananthapuram and Mumbai.

(iv) Name two stations with most extreme climate.

Answer Leh and Jodhpur.

(v) Name two stations most influenced by the Arabian branch of south-west monsoons.

Answer Mumbai and Thiruvananthapuram.

(vi) Name two stations most influenced by the Bay of Bengal branch of south-west monsoons.

Answer Shillong and Kolkata.

(vii) Name two stations influenced by both branches of the south-west monsoons.

Answer Delhi and Nagpur.

(viii) Name two stations influenced by retreating and north-east monsoons.

Answer Thiruvananthapuram and Chennai.

(ix) Name two stations receiving winter showers from the western disturbances.

Answer Delhi and Kolkata.

(x) Name two hottest stations in the months of

(a) February (b) April (c) May (d) June

Answer

(a) Thiruvananthapuram and Chennai.

(b) Nagpur and Chennai.

(c) Nagpur and Delhi / Jodhpur.

(d) Jodhpur and Delhi.

Q.4. Now find out

(i) Why are Thiruvananthapuram and Shillong rainier in June than in July?

Answer They are rainier in June as the monsoon’s arrival occurs in both places in June and the initial impact of the monsoon is an intense period of heavy rain.

(ii) Why is July rainier in Mumbai than in Thiruvananthapuram?

Answer The monsoon reaches Mumbai about 10 days after Thiruvananthapuram and so the initial impact of the monsoon continues into the next month. After the first initial downpour the monsoon falls into a steady pattern of raining for at least a couple of hours most days. So, it reduces in Thiruvananthapuram earlier than in Mumbai.

(iii) Why are south-west monsoons less rainy in Chennai?

Answer Chennai doesn’t receive much rain during the south-west monsoon, as the south of India (the states of Tamil Nadu, Karnataka, and Kerala) gets most of its rainfall from the north-east monsoon, from October to December.

(iv) Why is Shillong rainier than Kolkata?

Answer Shillong is in a hilly area and the hills trap the monsoon winds, so that Shillong becomes rainier than Kolkata.

(v) Why is Kolkata rainier in July than in June unlike Shillong which is rainier in June than in July?

Answer The monsoon reaches Shillong earlier than Kolkata (refer to the ‘Advancing Monsoon’ map in your textbook) and the initial impact is heavier than the later showers. So, Shillong is rainier in June while Kolkata is rainier in July.

(vi) Why does Delhi receive more rain than Jodhpur?

Answer Jodhpur is on the edge of the Thar Desert and by the time the monsoon winds reach it, most of their moisture is finished. Delhi is more east than Jodhpur and so it receives more rainfall.

Q.5. Now think why

(i) Thiruvananthapuram has equable climate?

Answer Thiruvananthapuram has equable climate because of be reasons

(a) It is on the sea coast. The moderating influence of the sea makes the climate equable.

(b) It is near to the equator. At the equator, all the seasons have similar temperatures and so this makes the climate equable.

(ii) Chennai has more rains only after the fury of monsoon is over in most parts of the country?

Answer Chennai receives most of its rainfall from the north-east monsoon, which gives rains mostly from October to December, and not the south-west monsoon. That is why Chennai gets most of its rainfall later than most other parts of the country.

(iii) Jodhpur has a hot desert type of climate?

Answer Jodhpur is in the extreme western part of India and so. When the monsoon winds reach it, they have exhausted their moisture. Further it is on the edge of the Thar Desert. That is why it has a hot desert type of climate.

(iv) Leh has moderate precipitation almost throughout the year?

Answer Leh is in the ‘cold desert’ called Ladakh, which is a valley in between two mountain ranges. No monsoon winds are able to reach it. That is why it has moderate precipitation almost throughout the year.

(v) While in Delhi and Jodhpur most of the rain is confined to nearly three months, in Thiruvananthapuram and Shillong it is almost nine months of the year?

Answer Thiruvananthapuram is on the sea coast and so it receives rainfall from both the southwest and north-east monsoons, besides receiving rainfall due to local disturbances which pick up moisture from the sea. Shillong is in a hilly area and so receives rain from the monsoon as well as from local disturbances which are trapped by the hills.

(vi) In spite of these facts see carefully if there are strong evidences to conclude that the monsoons still provide a very strong framework lending overall climatic unity to the whole country.

Answer The seasonal alteration of the wind systems and the associated weather conditions provide a rhythmic cycle of seasons. Monsoon rains are unevenly distributed and typically uncertain. The Indian landscape, plant and animal life, agriculture, the people and their festivities, all revolve around the monsoon.

All the Indian people eagerly await the arrival of the monsoon. It binds the whole country by providing water which sets all agricultural activities in motion. That is why the monsoon is considered a unifying bond.


Map Skills


Q.9. On an outline map of India, show the following.
(i) Areas receiving rainfall over 400 cm.
(ii) Areas receiving less than 20 cm of rainfall.
(iii) The direction of the South-West Monsoon over India.

Answer:


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