Planetary, Seasonal and Local Winds
Geography › Pressure, Winds and Atmospheric Moisture · Topic 7.5
Winds are of three kinds. Planetary or permanent winds, the trade winds, westerlies and polar easterlies, blow throughout the year over large areas. Seasonal or periodic winds, such as the monsoons and land and sea breezes, change direction with the season or the time of day. Local winds, such as the loo, foehn, chinook and mistral, arise from local heating, cooling or relief.
6 min read · UPSC Prelims · Geography · Pressure, Winds and Atmospheric Moisture
At a Glance
- Planetary Trades, westerlies, polar easterlies
- Seasonal Monsoons, land and sea breezes
- Local hot winds Loo, sirocco, khamsin, foehn, chinook
- Local cold winds Mistral, bora, buran
- Indian local winds Loo, Kalbaisakhi, mango showers
- Exam link UPSC Prelims, Geography: Pressure, Winds and Atmospheric Moisture
Where Does It Fit?
This is the fifth topic of the category on pressure, winds and atmospheric moisture. The previous topic gave the general circulation, and this one classifies the winds that result. The next topic begins the study of atmospheric moisture. Previous topic: General Circulation of the Atmosphere. Next topic: Water Vapour, Evaporation and Condensation.
What Are Planetary Winds?
In short: planetary winds are the steady winds of the global circulation.
| Wind | Belt | Direction | Features |
|---|---|---|---|
| Trade winds | Subtropical highs to the equatorial low, about 30 degrees north and south to the equator | Northeast in the north, southeast in the south | Steady and reliable; they bring rain to the eastern sides of continents, while the western sides are dry; used by sailors for trade |
| Westerlies | Subtropical highs to subpolar lows, about 30 to 60 degrees | Southwest in the north, northwest in the south | Bring rain to the western coasts of continents; stronger in the southern hemisphere, where they are called the roaring forties, furious fifties and shrieking sixties |
| Polar easterlies | Polar highs to subpolar lows | Northeast in the north, southeast in the south | Cold and dry |
The origin of these winds is described in General Circulation of the Atmosphere. The roaring forties are the westerlies between 40 and 50 degrees south, where there is almost no land to slow them.
What Are Seasonal Winds?
Seasonal or periodic winds change their direction with the seasons or with the time of the day because of the different heating of land and sea.
- Monsoons: winds that reverse their direction between summer and winter, blowing from the sea to the land in summer and from the land to the sea in winter. They are most marked in South and Southeast Asia, but also occur in East Africa, northern Australia and West Africa. The Indian monsoon is explained in Mechanism of the Indian Monsoon.
- Land and sea breezes: a daily reversal on coasts. By day, the land warms faster than the sea, air rises over the land and cooler air comes in from the sea as a sea breeze. At night the land cools faster, and the breeze blows from the land to the sea as a land breeze. They are common on the coasts of India, such as Mumbai and Chennai.
- Mountain and valley winds: by day the slopes warm, and air flows up the valley as an anabatic or valley wind; at night the cold dense air slides down the slope as a katabatic or mountain wind, filling the valley with cold air, as in Vertical Distribution of Temperature and Temperature Inversion.
What Are the Local Winds of the World?
| Wind | Region | Character |
|---|---|---|
| Loo | North and northwest India and Pakistan, in May and June | Very hot, dry, dusty day wind; can cause heatstroke |
| Foehn | Alps | Warm, dry wind descending the leeward slope; melts snow and ripens crops |
| Chinook | Eastern slopes of the Rockies | Warm, dry wind descending the lee slope; nicknamed the snow-eater |
| Mistral | Southern France, Rhône valley | Cold, strong, dry wind from the Alps to the Mediterranean |
| Bora | Adriatic coast | Cold, violent, dry wind |
| Sirocco | Sahara to southern Europe | Hot, humid or dusty wind, with sand |
| Harmattan | West Africa | Dry, dusty northeast trade wind that cools the humid coast; called the doctor |
| Khamsin | Egypt | Hot, dry, dusty wind of spring |
| Santa Ana | Southern California | Hot, dry wind that fans wildfires |
| Zonda | Argentina | Foehn-type wind on the Andes |
| Buran | Siberia and Central Asia | Cold winter wind with snow |
Foehn winds are produced when moist air rises on the windward side of a mountain, loses its moisture as rain and then descends on the leeward side, warming by compression at the dry adiabatic rate, which makes it warmer and drier than the air it replaced.
Which Local Winds and Storms Matter in India?
- Loo: the hot westerly wind of the northwestern plains in summer, which can raise temperatures above 45 degrees and cause heatstroke deaths; India now has heat action plans in many cities to cope with it.
- Kalbaisakhi (Nor’westers): violent thunderstorms with strong winds, rain and hail in Bengal, Jharkhand, Odisha and Assam in April and May; called Bordoichila in Assam.
- Mango showers: pre-monsoon showers in Kerala and Karnataka that help the ripening of mangoes.
- Blossom showers: pre-monsoon rain in Kerala and coastal Karnataka that benefits coffee flowers.
As an analytical point, local winds are important because they bring sudden changes in weather and affect health, farming and fire risk, and warm downslope winds such as the chinook and the Santa Ana show that the same physical process, compressional warming, can bring either benefit or hazard.
Why Is This Topic Important?
- Match-the-following Local winds asked in Prelims
- India Loo and Kalbaisakhi
- Concepts Breezes and foehn
What Came Next?
The next topic begins the study of atmospheric moisture and describes water vapour, evaporation and condensation. Next topic: Water Vapour, Evaporation and Condensation.
Key People and Terms
- Trade winds Steady tropical easterlies
- Monsoon Seasonal reversal of winds
- Sea breeze Day wind from sea to land
- Anabatic wind Upslope day wind
- Katabatic wind Downslope night wind
- Foehn Warm dry downslope wind
Exam Corner
Points to Remember
- Loo is the hot dry wind of north India.
- Chinook is the snow-eater of the Rockies.
- Mistral is a cold wind in France.
- Sea breeze blows by day; land breeze by night.
- Harmattan blows in West Africa.
Do Not Confuse With
- Anabatic and katabatic winds Up-valley day versus down-slope night
- Foehn and mistral Warm dry versus cold dry
- Planetary and seasonal winds Permanent versus reversing
Memory Hook
Loo burns, mistral chills, chinook melts the snow; sea breeze by day, land breeze by night.
Mains Angle
Questions ask for local winds and their effects. These points add depth.
- Origin Differential heating and relief
- Impact Weather, farming, health
- India Loo and nor’westers
A Question You May Face
An original practice question, not a past paper question.
“Classify winds and describe any four local winds with their effects on the regions where they blow.”
How to Answer
- Classify Planetary, seasonal, local.
- Local winds Hot and cold types.
- Effects On climate and life.
- India Loo and Kalbaisakhi.
GS Relevance
Frequently Asked Questions
What are the three types of winds?
Winds are classified into planetary or permanent winds, such as the trade winds, westerlies and polar easterlies; seasonal or periodic winds, such as monsoons and land and sea breezes; and local winds, such as the loo, foehn, chinook and mistral.
What are land and sea breezes?
Land and sea breezes are daily reversals of wind on coasts. By day the land heats faster, so cool air blows from the sea to the land as a sea breeze. At night the land cools faster, so the wind blows from the land to the sea as a land breeze.
What is the loo?
The loo is a hot, dry and dusty westerly wind that blows across northern and northwestern India and Pakistan in May and June. Temperatures can rise above 45 degrees Celsius, and it can cause heatstroke, so many Indian cities have heat action plans.
What is a foehn wind?
A foehn is a warm, dry wind that descends the leeward side of a mountain. Moist air loses its moisture as rain on the windward side, then warms by compression as it descends. The chinook of the Rockies and the Zonda of the Andes are similar winds.
What are Kalbaisakhi and mango showers?
Kalbaisakhi, or nor'westers, are violent pre-monsoon thunderstorms with winds and hail over Bengal, Odisha, Jharkhand and Assam in April and May. Mango showers are pre-monsoon rains in Kerala and Karnataka which help the ripening of mangoes.
PYQ Practice — Statement Analysis
1 The loo is a cold wind of northern India.
It is a hot, dry summer wind.
2 The chinook is a warm, dry wind on the eastern slopes of the Rockies.
It is called the snow-eater.
3 A sea breeze blows from the land to the sea.
It blows from the sea to the land.
4 The monsoon is a seasonal wind that reverses its direction.
It blows from sea to land in summer.
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