๐ Topic 04 of 6 ยท Chapter 03 ยท Climate of India
Rainfall Distribution in India
Highest/lowest rainfall areas, types of rainfall, state-wise distribution โ complete notes for UPSC & PSC exams.
๐ง๏ธ Rainfall Distribution โ Key Facts
| Category | Place | State | Rainfall |
|---|---|---|---|
| Highest average rainfall (world) | Mawsynram | Meghalaya | ~11,872 mm/year |
| 2nd highest (world record holder) | Cherrapunji (Sohra) | Meghalaya | ~11,430 mm/year |
| Highest rainfall state | Meghalaya | NE India | Bay of Bengal branch + Khasi Hills |
| Lowest rainfall place | Leh / Drass | Ladakh | <10 cm/year (rain shadow of Himalayas) |
| Driest state | Rajasthan | NW India | ~10โ20 cm/year (Thar Desert) |
| Highest rainfall in India (single year) | Cherrapunji | Meghalaya | 26,461 mm (1861) โ world record |
๐ง๏ธ Rainfall Zones of India
| Zone | Annual Rainfall | Areas |
|---|---|---|
| Very Heavy Rainfall | >200 cm | Western Ghats (windward), NE India, Andaman & Nicobar, West Bengal coast |
| Heavy Rainfall | 100โ200 cm | Eastern India, sub-Himalayan belt, Konkan coast, Malabar coast |
| Moderate Rainfall | 50โ100 cm | Deccan Plateau, UP, Bihar, Jharkhand, Odisha interior |
| Low Rainfall | 25โ50 cm | NW India, Rajasthan, Gujarat, Haryana, Punjab |
| Very Low Rainfall | <25 cm | Thar Desert (Rajasthan), Ladakh, Kachchh (Gujarat) |
๐ง๏ธ Types of Rainfall
| Type | Mechanism | Where in India |
|---|---|---|
| Orographic (Relief) Rainfall | Moist winds hit a mountain barrier โ forced to rise โ cool โ condense โ rain on windward side | Western Ghats (windward), Meghalaya hills, Himalayas |
| Convectional Rainfall | Ground heats up โ air rises โ cools โ condenses โ heavy rain with thunder | Interior Deccan Plateau in summer; tropical areas |
| Cyclonic (Frontal) Rainfall | Warm and cold air masses meet โ warm air rises over cold โ rain along fronts | NW India (Western Disturbances in winter); Bay of Bengal cyclones |
โญ Why does Rajasthan get so little rain?
1. Aravalli Mountains run parallel to the Arabian Sea branch of SW monsoon โ don’t block it
2. By the time Bay of Bengal branch reaches Rajasthan, it has lost most moisture
3. Hot desert surface โ air rises rapidly without condensing
4. Result: Thar Desert โ India’s largest desert
1. Aravalli Mountains run parallel to the Arabian Sea branch of SW monsoon โ don’t block it
2. By the time Bay of Bengal branch reaches Rajasthan, it has lost most moisture
3. Hot desert surface โ air rises rapidly without condensing
4. Result: Thar Desert โ India’s largest desert
๐ Variability of Rainfall:
โข Areas with low rainfall have high variability (unreliable) โ Rajasthan, Gujarat
โข Areas with high rainfall have low variability (reliable) โ Kerala, NE India
โข High variability = drought-prone areas = need irrigation
โข Areas with low rainfall have high variability (unreliable) โ Rajasthan, Gujarat
โข Areas with high rainfall have low variability (reliable) โ Kerala, NE India
โข High variability = drought-prone areas = need irrigation