UPSC Mains — Previous Year Question
Question
Compare the Loo, Chinook and Foehn winds with respect to their regions of prevalence, their nature and climatic impacts.
Model Answer
Local winds are regional-scale winds shaped by local temperature, pressure, and topography. Loo, Chinook, and Foehn exemplify such winds, differing in regions of prevalence, physical characteristics, and climatic impacts.
Comparison of Loo, Chinook and Foehn Winds
| Basis | Loo | Chinook | Foehn |
|---|---|---|---|
| Nature & Mechanism | • Hot, dry, dusty local wind. • Summer afternoon phenomenon. • Exceptionally high temperatures. • Extremely low humidity. | • Warm, dry downslope wind. • Adiabatically heated on leeward slopes. • Rapid temperature rise. • Known as “Snow Eater”. | • Warm, dry downslope wind. • Adiabatic compression warming. • Develops on the leeward Alpine side. • Strong, gusty, and desiccating. |
| Regions of Prevalence | • Northern and northwestern India. • Indo-Gangetic Plains: Rajasthan, Punjab, Haryana, Delhi, Uttar Pradesh, and Bihar. | • Eastern leeward slopes of the Rocky Mountains. • Western Canada and Great Plains of the USA. | • Leeward northern valleys of the Alps. • Switzerland, Austria, and southern Germany. |
| Climatic & Environmental Impacts | 1. Intensifies pre-monsoon heatwaves across northern India, causing extreme heat. 2. Causes drying effect; sharp fall in humidity increases evapotranspiration. 3. Severe soil moisture loss and agricultural stress. 4. Carries particulate dust, reducing local visibility and increasing discomfort. 5. Human Impact: Fatal heatstroke and severe dehydration are common. | 1. Rapid winter temperature rises within hours, providing relief from cold. 2. Accelerates snowmelt and reduces snow cover (known as snow eater). 3. Exposes pastures early, benefiting livestock ranching. 4. Sudden snowmelt increases local river runoff. 5. Hazards: Rapid snowpack thaw increases avalanche risk and damages vegetation. | 1. Produces unusually warm, dry microclimates north of the Alps (leeward warming). 2. Rapidly melts Alpine snow and shortens snow-cover duration. 3. Benefits agriculture by extending growing and grazing seasons in Alpine valleys. 4. Hazards: Rapid snowmelt and dry gusts increase avalanche and wildfire risks. |
“Local winds, regional consequences”: winds like the Loo, Chinook, and Foehn significantly shape regional microclimates, agriculture, and livelihoods, highlighting how local atmospheric processes produce far-reaching socio-economic impacts.