Briefly mention the alignment of major mountain ranges of the world and explain their impact on local weather conditions, with examples.
Approach · directive: “briefly mention / explain”
What it asks · First state the alignment of major ranges (east-west or north-south), then link that alignment to rainfall, temperature and wind patterns with examples.
It asks 2 things — answer each
- Briefly mention: the alignment of the world's major mountain ranges
- Explain: their impact on local weather (rain, rain shadow, winds, temperature, local circulation), with examples
Open with · Temperature falls with height at about 6.5°C per 1,000 m, and moist air forced up a slope cools until it rains, so a range's alignment to the prevailing winds decides local weather.
Cover
- East-west ranges (Himalaya, Alps, Pyrenees) separate air masses; north-south ranges (Rockies, Andes, Western Ghats) stand across westerlies, trades and monsoon.
- Orographic rain: the windward Western Ghats and west coast get 250-400 cm of monsoon rain.
- Rain shadow: the Deccan interior, Patagonia and the Great Basin stay dry behind ranges.
- Foehn and chinook: warm, dry winds from adiabatic compression on lee slopes of the Alps and Rockies.
- Barrier: the Himalaya blocks cold Central Asian air and holds the monsoon; Ladakh is a cold desert.
- Altitude and breezes: lapse rate zoning, valley and mountain breezes, inversions; Khasi Hills funnel rain over 1,080 cm.
Close with · Alignment, not height alone, decides where rain falls: a range across the wind divides wet from dry within a few dozen kilometres, so mountain planning must follow slope and aspect.
Add value (verified)
- Foehn: a warm, dry lee-side wind heated by adiabatic compression as air descends.Glossary: Foehn — NOAA National Weather Service ↗“A warm, dry wind on the lee side of a mountain range, the warmth and dryness of the air being due to adiabatic compression as the air descends the mountain slopes.”
- Chinook is the name for foehn winds in the lee of the Rocky Mountains.Glossary: Chinook — NOAA National Weather Service ↗“This is a region-specific term used for Foehn Winds in the lee of the Rocky Mountains in the United States”
Question: UPSC's CS (Main) 2021, GS Paper I — paper ↗. Approach: Minimalist IAS, checked 16 Oct 2026 (how we verify) — UPSC publishes no model answers. ·
Model answer· 327words · Minimalist IAS
Temperature falls with height at a normal lapse rate of 6.5°C per 1,000 m, and moist air forced up a slope cools until its vapour condenses. A range's alignment to the prevailing winds therefore decides where rain falls and how local weather behaves.
Alignment of major ranges
| Alignment | Major ranges | Winds they meet |
|---|---|---|
| East-west | Himalaya, Alps, Pyrenees | Polar and tropical air masses |
| North-south | Rockies, Andes, Urals, Western Ghats | Westerlies, trades, monsoon |
| South-west to north-east | Appalachians, Atlas, Aravali | Oblique, varied winds |
Impact on local weather
- Orographic rain: windward slopes force air up; the windward side of the Western Ghats and the west coast receive 250-400 cm of monsoon rain.
- Rain shadow: descending air warms and dries, so the Deccan interior behind the Ghats, Patagonia east of the Andes and the Great Basin behind the Sierra Nevada stay dry.
- Moist wind meets a range
- air rises and cools
- condensation, windward rain
- air descends and warms
- dry rain-shadow lee
- Foehn and chinook: warm, dry winds on lee slopes, heated by adiabatic compression as air descends; the chinook is the Rocky Mountain form, melting snow quickly.
- Climatic barrier: the east-west Himalaya blocks cold Central Asian air and holds monsoon clouds over the plains, leaving Ladakh a cold desert where winter temperatures fall to minus 45°C around Leh.
- Altitude zoning: the lapse rate gives high ranges a snowline, glaciers and vertical belts of climate and vegetation, as in the Alps, Andes and Himalaya.
- Mountain and valley breezes: slopes and valley floors heat and cool at different rates, driving daytime up-slope and night-time down-slope winds, with fog and frost pooling in valleys.
- Funnelled extremes: hills that trap moist winds concentrate rain; Cherrapunji and Mawsynram in the Khasi Hills receive over 1,080 cm a year, while Jaisalmer gets very little.
Alignment, not height alone, decides where rain falls: a range across the wind divides wet from dry within a few dozen kilometres, so watershed and disaster planning in mountains must follow slope and aspect.
Prepared by Minimalist IAS to the answer standard of Shivam Singh (mentor, 7 years) · facts checked against official sources (how we verify) · updated 16 Oct 2026. UPSC publishes no model answers: compare your structure and coverage with this, then write your own.
