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Climate – Class 11 Geography notes, important questions and MCQs

NCERT Class 11 Geography, chapter 18. Notes, key terms, important questions with answers and MCQs.

हिंदी में पढ़ें

Chapter overview

India has a monsoon type of climate, characterised by a seasonal reversal of winds. Within this, there are regional variations in temperature and rainfall. The climate is influenced by latitude, the Himalayas, the distribution of land and water, distance from the sea, altitude, relief, and upper air circulation such as jet streams and western disturbances. India has four seasons: the cold weather season, the hot weather season, the south-west monsoon season and the retreating monsoon season.

Factors and mechanism of the monsoon

  • Factors include latitude (the Tropic of Cancer), the Himalayas acting as a barrier to cold winds, the Indian Ocean, relief and the ITCZ.
  • The monsoon is linked to differential heating of land and sea, the northward shift of the ITCZ in summer, the westerly jet stream moving north of the Himalayas and the easterly jet stream over the peninsula, the Tibetan plateau heating, El Niño and the Indian Ocean Dipole.
  • The south-west monsoon usually reaches Kerala around 1 June, splits into the Arabian Sea and Bay of Bengal branches, and covers the country by mid-July; breaks in the monsoon are dry spells.

Seasons and rainfall distribution

  • The cold weather season (December–February) has clear skies, low temperatures in the north and some rain from western disturbances; Tamil Nadu gets rain from the north-east monsoon.
  • The hot weather season (March–May) has rising temperatures and local storms such as mango showers, Kal Baisakhi and loo.
  • The south-west monsoon (June–September) brings most of India's rainfall; the retreating monsoon (October–November) brings rain to the Coromandel coast and cyclones in the Bay of Bengal. Rainfall is highest in the Western Ghats and the north-east (Mawsynram) and lowest in western Rajasthan and Ladakh.

Key terms

Monsoon
seasonal reversal of wind direction
Western disturbances
low-pressure systems from the Mediterranean that bring winter rain to north-west India
Jet stream
a narrow belt of fast-moving winds in the upper atmosphere
Break in the monsoon
a dry spell during the rainy season
Kal Baisakhi
violent evening thunderstorms in Bengal and Assam in summer

Important questions with answers

What is a break in the monsoon?2 marks

A break in the monsoon is a period of dry weather lasting one or more weeks during the rainy season. It occurs when the monsoon trough moves north towards the Himalayas or when rain-bearing systems are weak.

Why does the Coromandel coast receive rain in winter?3 marks

In October–December, the retreating monsoon winds and the north-east monsoon blow from the north-east over the Bay of Bengal, picking up moisture. When they reach the Coromandel coast of Tamil Nadu, they bring rain, and cyclones from the Bay of Bengal add to it.

Explain the mechanism of the Indian monsoon.5 marks

The Indian monsoon is a seasonal reversal of winds, and several factors explain it. In summer, the land heats much faster than the surrounding seas, creating an intense low-pressure area over north-west India and Pakistan, while high pressure develops over the Indian Ocean. The Inter-Tropical Convergence Zone (ITCZ) shifts northward over the Ganga plain, and the south-east trade winds of the Southern Hemisphere cross the equator, are deflected by the Coriolis force and blow as south-west monsoon winds towards India. Upper air circulation is important: in summer the westerly jet stream shifts north of the Himalayas and an easterly jet stream develops over the peninsula, which helps the monsoon burst. The heating of the Tibetan plateau creates strong upward air currents that strengthen the circulation. The monsoon reaches Kerala around 1 June and splits into the Arabian Sea branch, which gives heavy rain to the Western Ghats, and the Bay of Bengal branch, which brings rain to the north-east and the Ganga plain. Its strength varies: El Niño, the warming of the eastern Pacific, often weakens the monsoon, while a positive Indian Ocean Dipole can strengthen it. In autumn, as the land cools and the ITCZ moves south, the winds reverse and the monsoon retreats.

Quick revision

  • Monsoon: seasonal reversal of winds.
  • Factors: latitude, Himalayas, ITCZ, jet streams, El Niño.
  • Onset in Kerala around 1 June; two branches.
  • Four seasons; rainfall distribution.

Exam tips

  • Make a table of the four seasons with months and features.
  • Learn the local storms: mango showers, blossom showers, Kal Baisakhi, loo.

Practice MCQs

  1. The monsoon is characterised by

    1. no change in wind
    2. seasonal reversal of winds
    3. constant rain all year
    4. snowfall everywhere
    Show answer

    Answer: (b) seasonal reversal of winds. Winds change direction with seasons.

  2. The south-west monsoon usually reaches Kerala around

    1. 1 March
    2. 1 June
    3. 15 August
    4. 1 October
    Show answer

    Answer: (b) 1 June. It then advances northward.

  3. The hot dry winds of north India in summer are called

    1. Kal Baisakhi
    2. nor'westers
    3. mango showers
    4. loo
    Show answer

    Answer: (d) loo. They blow in the afternoon.

  4. Winter rain in north-west India is mainly due to

    1. south-west monsoon
    2. western disturbances
    3. tropical cyclones
    4. retreating monsoon
    Show answer

    Answer: (b) western disturbances. They come from the Mediterranean.

  5. Tamil Nadu receives most of its rain in

    1. October–December
    2. June–July
    3. March–April
    4. January only
    Show answer

    Answer: (a) October–December. It is from the north-east and retreating monsoon.

  6. Pre-monsoon showers that help ripen mangoes in Kerala and Karnataka are called

    1. Kal Baisakhi
    2. mango showers
    3. loo
    4. blossom showers of Kashmir
    Show answer

    Answer: (b) mango showers. They occur in April–May.

  7. Which factor helps the onset of the south-west monsoon

    1. southward shift of the ITCZ
    2. absence of the Himalayas
    3. cooling of Tibet
    4. northward shift of the ITCZ and the easterly jet over the peninsula
    Show answer

    Answer: (d) northward shift of the ITCZ and the easterly jet over the peninsula. The westerly jet also moves north of the Himalayas.

  8. El Niño years are often associated with

    1. excess rainfall in India
    2. weak or deficient monsoon in India
    3. no change
    4. snowfall in Kerala
    Show answer

    Answer: (b) weak or deficient monsoon in India. Warming of the eastern Pacific disturbs circulation.

All chapters of Class 11 Geography

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.