Climate — Practice

Question 1

Define climate.

Accepted Answer

Step 1 — Define.
  Climate is the long-term average pattern of weather conditions (temperature, rainfall, humidity, wind) at a specific place, measured over many years (typically 30+ years).

Step 2 — Distinguish from weather.
  Weather is short-term — what conditions are at a specific moment.
  Climate is the long-term average.

✦ Answer: Climate is the long-term average of weather conditions over many years (30+ years). Weather is the short-term condition.

Question 2

Name the four seasons of India and their months.

Accepted Answer

Step 1 — Recall.
  1. Cold weather season (winter): December to February.
  2. Hot weather season (summer): March to May.
  3. South-West monsoon season (rainy): June to September.
  4. Retreating monsoon season (autumn): October to November.

Step 2 — Note.
  Some classifications combine months differently. CBSE typically uses these four.

✦ Answer: Cold (Dec-Feb), Hot (Mar-May), South-West Monsoon (Jun-Sep), Retreating Monsoon (Oct-Nov).

Question 3

What is the cause of the Indian monsoon?

Accepted Answer

Step 1 — Underlying cause.
  The Indian monsoon is caused by DIFFERENTIAL HEATING OF LAND AND SEA.

Step 2 — Details.
  In summer, the Indian subcontinent heats up faster than the Indian Ocean. This creates LOW PRESSURE over land. Cooler air from the ocean (HIGH PRESSURE) rushes inland — bringing moisture and rain. This is the south-west monsoon.
  In winter, the reverse happens: land cools faster, creating high pressure that pushes air OUT to sea — bringing dry conditions to most of India.

✦ Answer: The differential heating of land and sea. Land heats faster than sea in summer, creating low pressure over India that draws moist air in from the Indian Ocean — the south-west monsoon.

Question 4

Which is the wettest place in India? Why?

Accepted Answer

Step 1 — Identify.
  Mawsynram in Meghalaya, India.

Step 2 — Rainfall.
  ~11,872 mm/year on average. The wettest place on Earth.
  Cherrapunji (also in Meghalaya, very nearby) was the previous record-holder.

Step 3 — Why so wet.
  • Located in the path of Bay of Bengal monsoon branch.
  • Mountains (Khasi Hills) cause orographic rainfall.
  • Funnel-shaped valley concentrates rain.
  • Tropical location maximises moisture.

✦ Answer: Mawsynram (Meghalaya, NE India) with ~ 11,872 mm/year. Heavy rain because the Bay of Bengal monsoon hits the Khasi Hills, causing extreme orographic rainfall.

Question 5

What is 'Loo'?

Accepted Answer

Step 1 — Define.
  Loo is a hot, dry wind blowing across the Northern Indian Plains during the summer (April-June).

Step 2 — Origin.
  Originates from the western desert regions (Iran, Iraq, Afghanistan, Pakistan, Rajasthan).

Step 3 — Characteristics.
  • Very hot — can reach 50°C.
  • Dry — no moisture content.
  • Dust-laden.
  • Dangerous to health (causes heat stroke).

✦ Answer: Loo is a hot, dry wind blowing from the western desert regions across the Indian plains during summer. Can reach 50°C; very dangerous to outdoor workers.

Question 6

Explain how the Himalayas affect India's climate.

Accepted Answer

Step 1 — Block cold Central Asian air.
  The Himalayas physically block bitter cold winds from Central Asia in winter. Without them, North India would be as cold as Mongolia or northern China in winter — too cold for the dense Indian agriculture-based population.
  Because of the Himalayas, North India's winters are cool (5-15°C) but not extreme.

Step 2 — Trap monsoon rains.
  In summer, the south-west monsoon winds bring moisture from the Indian Ocean. The Himalayas force these winds to rise and cool — causing massive rainfall on the southern slopes (and into the Northeast). The rivers of North India are fed by this rainfall.
  Without the Himalayas, the rains would just blow across the plains to Central Asia.

Step 3 — Create snow and glaciers.
  Above ~4,000 m, the Himalayas have permanent snow and glaciers. These store water in winter and slowly release it as snowmelt in summer — keeping rivers like the Indus and Ganga PERENNIAL.

Step 4 — Create rain shadows.
  Areas in the rain shadow of the Himalayas (e.g., Ladakh, Spiti, Tibet) are very dry — cold deserts. This is a direct effect of the Himalayas blocking moisture.

Step 5 — Affect regional temperatures.
  Areas higher in altitude in the Himalayas (Kashmir Valley, Himachal Pradesh) have temperate climates — cool summers, cold winters. Specific microclimates exist.

✦ Answer: The Himalayas: (i) block cold Central Asian winds, keeping North India's winter mild; (ii) trap monsoon rains, providing water for North Indian rivers; (iii) store water as snow/glaciers feeding perennial rivers; (iv) create rain shadows (Ladakh cold desert); (v) create temperate microclimates at higher altitudes. They are arguably the single most important climatic feature of India.

Question 7

Describe the south-west monsoon's progression from Kerala to North India.

Accepted Answer

Step 1 — Kerala (June 1 ~).
  Monsoon strikes Kerala first, around June 1. Called the 'burst of monsoon.'
  Causes intense rainfall on the Western Ghats and along the Malabar Coast.
  Lasting heavy rains begin.

Step 2 — Mumbai and Maharashtra (June 10 ~).
  About 10 days later, monsoon reaches Mumbai. Massive rainfall on the Konkan Coast.
  Mumbai gets ~2,200 mm of rain over June-September.

Step 3 — Northern plains (late June - early July).
  Monsoon reaches Delhi by June 25-29.
  Reaches Punjab and Haryana in early July.
  Major rainfall now spread across North India.

Step 4 — Northeast (June 7 ~).
  Bay of Bengal branch reaches the Northeast (Assam, Meghalaya) by June 7-10.
  Causes heavy rainfall on Khasi-Jaintia hills (Mawsynram, Cherrapunji).

Step 5 — Withdrawal.
  Monsoon starts WITHDRAWING from Northwest India in mid-September.
  Withdrawal continues over October. By late October, all of India is largely dry.
  Note: 'withdrawal' is gradual — different from the rapid onset.

Step 6 — Coverage.
  By mid-July, the entire country is covered by the south-west monsoon (with Tamil Nadu being the exception — Tamil Nadu gets the NORTHEAST monsoon in winter, not the south-west monsoon).

✦ Answer: South-west monsoon arrives in Kerala around June 1 (burst), reaches Mumbai by June 10, Delhi by June 25-29, Punjab/Haryana by early July. Bay of Bengal branch reaches Northeast around June 7. Monsoon withdraws from Northwest India in mid-September and gradually retreats by late October.

Question 8

Why does Tamil Nadu receive most of its rainfall in October-November (retreating monsoon)?

Accepted Answer

Step 1 — South-West monsoon doesn't reach Tamil Nadu effectively.
  The south-west monsoon (June-September) brings rain to the WEST COAST (Kerala, Karnataka, Maharashtra) — but the WESTERN GHATS BLOCK most of these winds from crossing to Tamil Nadu.
  By the time monsoon air reaches Tamil Nadu, most moisture has been deposited as rain on the Western Ghats.
  Result: Tamil Nadu interior gets relatively little rainfall in June-September.

Step 2 — Retreating monsoon brings rain to Tamil Nadu.
  In October-November, the south-west monsoon RETREATS. As it withdraws, air picks up moisture from the Bay of Bengal.
  This north-east-flowing wind (now called the north-east monsoon) sweeps across the Bay of Bengal.
  When it hits the eastern coast (especially the south-eastern coast — Coromandel Coast in Tamil Nadu), it brings RAINFALL.

Step 3 — Specific Tamil Nadu mechanism.
  • Bay of Bengal is still warm in October-November (sea takes longer to cool than land).
  • Air over Bay of Bengal picks up moisture.
  • Tamil Nadu's eastern coast lies in the path of these moisture-laden winds.
  • Hence Tamil Nadu's October-December rainfall.

Step 4 — Cyclones.
  Same Bay of Bengal warmth produces cyclones — many of which strike the Tamil Nadu/Andhra coast in October-November.

Step 5 — Result.
  Tamil Nadu coastal region is the only region in India where the bulk of annual rainfall comes in the RETREATING monsoon (winter), not the south-west monsoon (summer).

✦ Answer: Tamil Nadu gets little rain from the south-west monsoon because the Western Ghats block these winds. But during the retreating monsoon (October-November), winds blowing from the warm Bay of Bengal pick up moisture and strike the Tamil Nadu (Coromandel) coast — bringing heavy rainfall and occasional cyclones.

Question 9

How does El Niño affect the Indian monsoon?

Accepted Answer

Step 1 — What is El Niño?
  El Niño is a periodic (3-7 years) warming of the surface waters of the central and eastern Pacific Ocean. It alters atmospheric circulation across the entire Pacific basin.

Step 2 — Effect on Indian monsoon.
  El Niño tends to WEAKEN the Indian summer monsoon.
  Mechanism:
  • Warm Pacific water disrupts global wind patterns.
  • The Indian Ocean becomes RELATIVELY cooler compared to the Pacific.
  • This reduces the temperature contrast that drives the Indian monsoon.
  • Less monsoon rain reaches India.

Step 3 — Historical examples.
  Major El Niño years (with deficient Indian monsoon):
  • 1997-98: severe El Niño.
  • 2002: drought in India.
  • 2009: drought in India.
  • 2014-15: major El Niño.
  • 2023: significant El Niño.

Step 4 — Result for India.
  El Niño years often see:
  • Below-average rainfall.
  • Crop failures (especially rice, soybean).
  • Higher food prices.
  • Drought in many regions.
  • Hydroelectric output reduction.

Step 5 — La Niña — the opposite.
  La Niña is the COOLING of Pacific surface waters. It tends to STRENGTHEN the Indian monsoon. La Niña years often have above-average rainfall in India.

Step 6 — Predictability.
  El Niño/La Niña patterns are now predictable several months in advance. The Indian Meteorological Department uses these forecasts to inform agriculture, water, and energy planning.

✦ Answer: El Niño (Pacific Ocean warming) tends to WEAKEN the Indian monsoon. The temperature contrast that drives the monsoon is reduced. Result: less rainfall, droughts, crop failures. Major El Niño years (1997, 2002, 2009, 2014, 2023) all had below-average Indian monsoons.

Question 10

Why are Cherrapunji and Mawsynram so much wetter than the rest of India?

Accepted Answer

Step 1 — Geographic location.
  Both are in Meghalaya (Northeast India), in the Khasi-Jaintia Hills.
  They sit in a funnel-shaped valley between two mountain ridges.

Step 2 — Bay of Bengal monsoon path.
  The Bay of Bengal branch of the south-west monsoon sweeps northward across India. As it reaches Northeast India, it encounters the Khasi Hills.

Step 3 — Orographic uplift.
  The hills FORCE the moist monsoon winds to rise.
  As air rises, it cools.
  Cool air can hold less moisture, so water vapour condenses into clouds and rain.
  This is OROGRAPHIC RAINFALL — very intense.

Step 4 — Funnel effect.
  The valleys around Mawsynram have a funnel shape that concentrates moisture-laden winds. Air is squeezed into narrower passes, intensifying both wind speed and the orographic uplift.

Step 5 — Rainfall figures.
  Mawsynram: ~ 11,872 mm/year average — the wettest place on Earth.
  Cherrapunji: ~ 11,777 mm/year average — second wettest.
  These places can receive over 1 m of rain in a SINGLE DAY during peak monsoon.

Step 6 — Contrast with the rest of India.
  Most of India gets 500-1500 mm/year. The Thar Desert gets <100 mm.
  The extreme rainfall in Meghalaya is the combination of:
  • Specific geographic location (funnel valley).
  • Path of Bay of Bengal monsoon branch.
  • Orographic uplift.
  These factors don't occur together elsewhere in India.

✦ Answer: Cherrapunji and Mawsynram receive extreme rainfall because the Bay of Bengal monsoon hits the Khasi Hills (orographic uplift) in a funnel-shaped valley (concentrating moisture). Average annual rainfall ~11,000+ mm — the highest in the world.

Question 11

Describe the four seasons of India in detail.

Accepted Answer

Step 1 — Cold weather season (December - February).

Temperature:
  • Northern Plains: cold; mean temperature 10-15°C. Frost and fog common in December-January.
  • Southern India: warm; mean temperature 20-30°C.
  Wind pattern: North-easterly trade winds.
  Pressure: HIGH pressure over land (Eurasia is cold); LOW pressure over Indian Ocean.
  Rainfall: Generally low. Exceptions:
  • Western disturbances (weather systems from Mediterranean) bring winter rain to North India (Punjab, Haryana, UP, Bihar) and snow to the Himalayas.
  • Tamil Nadu coast gets some rain from north-east monsoon residuals.
  Phenomena: Loo precursor weakening. Festivals: Diwali (November).

Step 2 — Hot weather season (March - May).

Temperature: Rises rapidly.
  • Northern Plains: very hot; daytime temperatures 40-45°C, sometimes >50°C in Rajasthan.
  • Southern India: warm; 30-35°C.
  Wind pattern:
  • LOO: hot, dry north-westerly wind blowing across the Northern Plains.
  • Westerly disturbances continuing.
  Pressure: LOW pressure developing over Northern India (heat).
  Rainfall:
  • Pre-monsoon thunderstorms ('Norwesters'/Kalbaisakhi) in West Bengal — short, intense, often damaging.
  • Pre-monsoon mango showers in Kerala/Karnataka.
  • Tamil Nadu gets sporadic rainfall.
  Phenomena: Dust storms, droughts, heat waves. Festivals: Holi (March).

Step 3 — South-West Monsoon season (June - September).

This is the DEFINING SEASON. Brings ~80% of India's annual rainfall.
  Onset:
  • Kerala (~June 1) — 'burst of monsoon.'
  • Mumbai (~June 10).
  • Delhi/North India (~June 25-July 1).
  • Northeast (~June 7).
  Wind pattern: South-westerly winds from Indian Ocean (high pressure) flow to India (low pressure).
  Branches:
  • Arabian Sea branch — strikes Western Ghats; heavy rain on west coast.
  • Bay of Bengal branch — strikes east coast and turns inland; rain in Bengal, Northeast, UP.
  Temperature: 30-40°C, but with high humidity; feels even hotter.
  Pressure: LOW pressure over Indian land continues.
  Rainfall: Heavy and seasonal. ~ 80% of annual rainfall in 4 months.
  Phenomena: Floods, landslides, monsoon festivals (Onam in Kerala).

Step 4 — Retreating Monsoon season (October - November).

Temperature: Decreasing. 25-35°C in North; 25-30°C in South.
  Wind pattern: Winds REVERSE. South-westerly winds withdraw; north-easterly winds become dominant.
  Pressure: HIGH pressure starting to develop over Northern India (cooling); LOW pressure over warm Bay of Bengal.
  Rainfall:
  • Most of India: dry.
  • Tamil Nadu coast: heavy rainfall (north-east monsoon).
  • Andhra Pradesh, Odisha: rainfall and cyclones from Bay of Bengal.
  Phenomena: Cyclones in Bay of Bengal (Phailin 2013, Hudhud 2014, Amphan 2020). Festivals: Diwali (October-November), Pongal (in early January, transition season).

Step 5 — Annual rainfall budget.
  Most regions: 80% of annual rainfall from south-west monsoon. Tamil Nadu: 60-70% from retreating monsoon. Northeast India: high rainfall in both seasons.

✦ Answer: India's four seasons:
(i) Cold (Dec-Feb): cool in North, warm in South, low rainfall except western disturbances.
(ii) Hot (Mar-May): scorching summer (40-45°C), Loo winds, pre-monsoon thunderstorms.
(iii) South-West Monsoon (Jun-Sep): defining season, 80% of annual rainfall, wind reversal from sea.
(iv) Retreating Monsoon (Oct-Nov): south-west monsoon withdraws, Tamil Nadu gets north-east monsoon, Bay of Bengal cyclones.

Question 12

How is climate change affecting Indian climate today, and what are the projections for the future?

Accepted Answer

Step 1 — Observed changes (1900-2024).

(a) Temperature rise.
  India's average temperature has risen by approximately 0.6°C since 1900. Summer temperatures are rising faster than winter temperatures. Heatwaves are more frequent and more intense.

(b) Monsoon variability.
  The monsoon is becoming MORE VARIABLE — same total rainfall but distributed less evenly. More extreme rainfall events (urban flooding) and more dry spells (drought).

(c) Glacier retreat.
  Himalayan glaciers (which feed the Indus, Ganga, Brahmaputra) are shrinking. Gangotri Glacier is retreating ~ 22 m per year. This affects long-term water availability.

(d) Sea-level rise.
  Indian coasts are seeing slow sea-level rise (~ 3 mm/year). Sundarbans is threatened. Mumbai, Chennai, Kolkata at risk of flooding.

(e) Cyclones intensifying.
  Bay of Bengal cyclones are getting more intense. Amphan (2020), Fani (2019), Phailin (2013), Hudhud (2014) — all major cyclones in recent years.

Step 2 — Recent specific events.
  • Delhi heatwave 2024: record-breaking 50°C+ in some areas.
  • Kerala floods 2018: catastrophic monsoon flooding.
  • Chennai water crisis 2019: 'Day Zero' nearly reached.
  • Cyclone Amphan 2020: most damaging Indian cyclone in 20 years.
  • Sundarbans erosion: 22% of Bangladesh's portion already lost.

Step 3 — Projections (2030-2100).

• Average temperature: increase 1-3°C by 2050; 2-5°C by 2100.
  • Heatwaves: more frequent, more intense.
  • Monsoon: variability increases; total rainfall may slightly increase but with worse extremes.
  • Sea-level rise: 0.5-1 m by 2100; major impact on coastal cities and Sundarbans.
  • Glacier ice: 30-50% loss by 2100.
  • Crop productivity: rice and wheat yields likely to decrease.
  • Diseases: vector-borne diseases (malaria, dengue) shifting to new regions as climates shift.

Step 4 — Vulnerability factors.
  India is particularly vulnerable because:
  • Large population dependent on agriculture (60% of workforce).
  • Highly populated coast (Mumbai, Chennai, Kolkata, Visakhapatnam).
  • Dependent on Himalayan rivers (for irrigation, drinking water).
  • Tropical location means relatively small temperature increases produce serious heat stress.

Step 5 — India's climate response.

(a) International commitments.
  • Net-zero emissions by 2070 (announced 2021 at COP26).
  • Renewable energy target: 500 GW by 2030.
  • Reduce carbon intensity by 45% by 2030.

(b) National Action Plan on Climate Change (NAPCC) — 2008.
  Includes 8 missions: solar, energy efficiency, sustainable agriculture, water, etc.

(c) International Solar Alliance.
  Launched by India at COP21 in Paris (2015). Aims to mobilise solar investments globally.

(d) Climate adaptation.
  Drought-resistant crops, water harvesting, urban flood management, coastal protection.

Step 6 — What more needs to be done.
  • Faster emissions reduction.
  • More renewable energy deployment.
  • Better adaptation infrastructure.
  • Climate-aware urban planning.
  • International cooperation (especially with neighbouring countries on shared waters).

✦ Answer: India is experiencing climate change rapidly. Observed: 0.6°C temperature rise since 1900, more variable monsoons, glacier retreat, sea-level rise, intensifying cyclones. Projections: 1-5°C further warming by 2100, more extreme weather, crop yield declines, coastal flooding. India is vulnerable but committed to net-zero by 2070 and renewable energy expansion (500 GW by 2030). National Action Plan on Climate Change (NAPCC) launched in 2008. Climate adaptation and emissions reduction are both essential.

Practice — Climate

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