Climate and Monsoons of India
Overview
India's climate is predominantly monsoon-type, influenced by the Himalayas, Indian Ocean, Arabian Sea, and Bay of Bengal. The country experiences four distinct seasons. The southwest monsoon brings about 75–90% of annual rainfall between June and September. Understanding pressure belts, jet streams, El Niño, La Niña, and regional rainfall patterns is essential for UPSC and BPSC examinations, as questions appear regularly on monsoon mechanisms, seasons, and climatic anomalies.
Typed Notes
Seasons of India
India experiences four seasons. Winter (December–February) is marked by cold northeasterly winds and clear skies; Tamil Nadu receives rainfall from the Northeast Monsoon during this period. Pre-monsoon/Summer (March–May) sees high temperatures (up to 48°C in Rajasthan), dust storms (Andhi), Nor'westers (Kalbaisakhi) in West Bengal, and Mango showers in Kerala and Karnataka. The Southwest Monsoon (June–September) accounts for 75–90% of annual rainfall. The Retreating Monsoon (October–November) causes cyclones in the Bay of Bengal and rainfall over the Coromandel Coast.
Mechanism of Southwest Monsoon
The Southwest Monsoon originates due to differential heating of land and sea. By June, a strong low-pressure area develops over the Thar Desert (Rajasthan), attracting moisture-laden winds from the Indian Ocean. The Inter-Tropical Convergence Zone (ITCZ) shifts northward. The Somali Jet and Tibetan Plateau heating intensify the monsoon. The Arabian Sea branch reaches Kerala around June 1 and covers the entire country by July 15. The Bay of Bengal branch enters Assam first, then moves westward. The Western Ghats cause orographic rainfall on the windward side.
Rainfall Distribution and Regional Patterns
India's rainfall is unevenly distributed. The Western Ghats windward side (Konkan, Goa, Kerala) receives over 250 cm annually, while the leeward side (Deccan Plateau) is a rain shadow receiving less than 50 cm. Northeast India (Assam, Meghalaya) gets the highest rainfall. Rajasthan, Ladakh, and parts of Gujarat are driest. The Coromandel Coast (Tamil Nadu, Andhra) gets most rain during October–December from the Northeast Monsoon. The concept of 'Normal Rainfall' is defined by IMD as the 50-year average. India's average annual rainfall is about 119 cm.
El Niño, La Niña, and Indian Ocean Dipole
El Niño refers to the periodic warming of central and eastern Pacific Ocean waters, which weakens the Walker Circulation and reduces Indian monsoon rainfall, causing drought. La Niña is the opposite — cooling of the Pacific — which strengthens the monsoon and may cause floods. The Indian Ocean Dipole (IOD) also affects monsoon: a positive IOD (warmer western Indian Ocean) enhances rainfall over India. The Southern Oscillation is the atmospheric component of El Niño; together they are called ENSO. IMD uses these indices for long-range monsoon forecasting.
Key Concepts
Revision ke liye ek nazar — exam se pehle yahi padhna hai.
- 01India has four seasons: Winter (Dec–Feb), Pre-monsoon/Summer (Mar–May), Southwest Monsoon (Jun–Sep), and Retreating Monsoon (Oct–Nov).
- 02The Southwest Monsoon has two branches: Arabian Sea branch (hits Kerala first, ~1 June) and Bay of Bengal branch (enters Northeast India first).
- 03The Coriolis force deflects winds to the right in the Northern Hemisphere, converting SE trade winds into SW monsoon winds.
- 04El Niño (warming of Pacific) weakens Indian monsoon; La Niña (cooling of Pacific) strengthens it — directly linked to drought/flood years.
- 05Mawsynram (Meghalaya) receives the highest average annual rainfall (~11,871 mm); Leh (Ladakh) is the driest region of India.
Questions & Solutions
Pehle khud try karo — phir solution kholo. Yahi tariqa topper banata hai.
Why does the Coromandel Coast receive rainfall during winter while the rest of peninsular India is dry?
Explain the role of the Western Ghats in creating a rain shadow region.
What is the Indian Ocean Dipole (IOD) and how does it influence Indian monsoon?
Distinguish between the Arabian Sea branch and Bay of Bengal branch of the Southwest Monsoon.
What is the significance of the Tibetan Plateau in the onset of the Indian Southwest Monsoon?
India's monsoon climate is driven by seasonal pressure differences, ITCZ movement, jet streams, and ocean temperature anomalies. The Southwest Monsoon (June–September) is the lifeline of Indian agriculture. Four distinct seasons shape regional weather. El Niño weakens and La Niña strengthens the monsoon. Mawsynram is wettest; Leh is driest. The Coromandel Coast is unique in receiving winter rainfall from the Northeast Monsoon — a frequently tested UPSC/BPSC fact.
Chapter-end quiz
4 MCQsOption tap karo — turant pata chalega sahi ya galat, explanation ke saath.
Q1.Which of the following places receives the highest average annual rainfall in India?
Q2.El Niño is associated with which of the following effects on Indian monsoon?
Q3.The 'Kalbaisakhi' (Nor'westers) storms are associated with which region and season?
Q4.Which of the following statements about the Northeast Monsoon is correct?
Mark karo — dashboard par progress dikhega.