Atmosphere, Winds, Pressure Belts, Clouds and Cyclones: Climatology Notes for SSC Geography
Rahul Kumar
SSC Exam Expert & Content Editor
In this note
- 1.Composition of the Atmosphere
- 2.Layers of the Atmosphere
- 3.Heat and Temperature
- 4.Pressure Belts
- 5.Planetary Winds
- 6.Seasonal and Local Winds
- 7.Clouds
- 8.Types of Rainfall
- 9.Cyclones
- 10.Tricks to Remember
- 11.Quick Tips
- 12.Quick Revision Points
- 13.Practice Questions With Answers
- 14.How to Practise This Chapter
- 15.Frequently Asked Questions
PDF Notes: Atmosphere, Winds, Pressure Belts, Clouds and Cyclones: Climatology Notes for SSC Geography
Premium PDF · one-time payment of ₹5 · instant access
The atmosphere, the winds and the weather are the standard topics of climatology in SSC geography. This guide on atmosphere, winds and pressure belts for SSC covers the layers of the atmosphere, the composition of air, the pressure belts, the planetary, seasonal and local winds, the types of clouds and rainfall and the cyclones, with practice questions and FAQs.
Composition of the Atmosphere
| Gas | Percentage by Volume |
|---|---|
| Nitrogen | 78% |
| Oxygen | 21% |
| Argon | 0.93% |
| Carbon dioxide | About 0.04% |
| Others (neon, helium, ozone, water vapour) | Very small |
Layers of the Atmosphere
| Layer | Height | Features |
|---|---|---|
| Troposphere | 0 to 8 km (poles) and 18 km (equator) | Contains almost all the weather, clouds and water vapour; temperature falls with height (6.5°C per km) |
| Stratosphere | Up to about 50 km | Contains the ozone layer (15 to 35 km), which absorbs ultraviolet rays; jet aircraft fly here; free from clouds |
| Mesosphere | Up to about 80 km | Coldest layer; meteors burn here |
| Thermosphere (ionosphere) | Up to about 600 km | Reflects radio waves; the aurora occurs here; temperature rises |
| Exosphere | Above 600 km | Merges with space |
Heat and Temperature
- The sun’s energy received by the earth is called insolation.
- Albedo is the percentage of sunlight reflected by a surface; ice and snow have the highest albedo.
- The greenhouse effect is the warming caused by gases such as carbon dioxide, methane and water vapour that trap heat; the main greenhouse gas is water vapour, and the main man-made one is carbon dioxide.
- Temperature decreases with height in the troposphere (normal lapse rate); in an inversion of temperature, it rises with height.
- The highest recorded air temperature is from Death Valley (USA); the lowest recorded temperature is from Vostok station in Antarctica.
Pressure Belts
| Belt | Latitude | Feature |
|---|---|---|
| Equatorial low pressure belt (doldrums) | 0° to 5° | Calm; hot; heavy convectional rainfall |
| Subtropical high pressure belts (horse latitudes) | 30° N and S | Dry; deserts; calm |
| Subpolar low pressure belts | 60° N and S | Stormy; cyclones |
| Polar high pressure belts | 90° N and S | Cold; very high pressure |
Planetary Winds
| Wind | Direction and Features |
|---|---|
| Trade winds | Blow from the subtropical highs to the equatorial low; north-east in the northern hemisphere, south-east in the southern; steady and dependable |
| Westerlies | Blow from the subtropical highs to the subpolar lows from the west; strongest in the southern hemisphere: Roaring Forties (40°S), Furious Fifties (50°S), Screaming Sixties (60°S) |
| Polar easterlies | Cold winds blowing from the polar highs to the subpolar lows |
- Winds are deflected to the right in the northern hemisphere and to the left in the southern hemisphere because of the Coriolis force (Ferrel’s law).
- Winds are named after the direction from which they blow.
- The speed of wind is measured with an anemometer; the direction with a wind vane; pressure with a barometer.
Seasonal and Local Winds
| Wind | Place | Features |
|---|---|---|
| Monsoon | India, South-East Asia | Seasonal reversal of wind direction |
| Loo | North India, Pakistan | Hot, dry wind in summer afternoons |
| Kalbaisakhi (Norwesters) | Bengal, Assam | Thunderstorms in April–May |
| Mango showers | Kerala, Karnataka | Pre-monsoon showers that help the ripening of mangoes |
| Chinook | Rocky Mountains (USA, Canada) | Warm, dry; “snow-eater” |
| Foehn | Alps (Europe) | Warm, dry wind |
| Mistral | France | Cold, dry wind from the Alps |
| Harmattan | West Africa (Sahara) | Hot, dry wind; called the “doctor” for its healthy effect |
| Sirocco | Sahara to the Mediterranean | Hot, dust-laden |
| Santa Ana | California | Hot, dry wind |
| Bora | Adriatic Sea | Cold, dry wind |
Clouds
| Cloud | Features |
|---|---|
| Cirrus | High (6 to 12 km); thin and wispy; ice crystals |
| Cumulus | Puffy, cotton-like; fair weather |
| Stratus | Low, layered, grey; drizzle |
| Nimbus (Cumulonimbus) | Dark, rain-bearing; thunderstorms |
| Altocumulus, Altostratus | Medium-height clouds |
Types of Rainfall
| Type | Cause | Example |
|---|---|---|
| Convectional | Heating of the ground makes warm air rise, cool and condense | Equatorial regions; afternoon showers |
| Orographic (relief) | Moist air rises over mountains | Western Ghats; windward side of the Himalayas; the leeward side is a rain-shadow area |
| Cyclonic (frontal) | Warm air rises over cold air at a front or in a cyclone | Temperate regions; the north-west of India in winter |
Cyclones
| Name | Region |
|---|---|
| Hurricane | Atlantic Ocean and the Caribbean, USA |
| Typhoon | Western Pacific, China Sea, Japan, the Philippines |
| Cyclone | Bay of Bengal and the Arabian Sea (Indian Ocean) |
| Willy-willies | Northern Australia |
| Tornado | USA; a very violent whirlwind on land |
- A tropical cyclone has a low-pressure centre called the eye, which is calm.
- Tropical cyclones form over warm seas (above 26.5°C); they weaken on land.
- In India, the cyclones are named by a list prepared by the countries around the Indian Ocean under the World Meteorological Organization.
- An anticyclone has high pressure at the centre and clear weather.
Tricks to Remember
- Weather occurs in the troposphere; ozone is in the stratosphere.
- The Coriolis force makes winds turn right in the north and left in the south.
- Chinook = snow-eater; Harmattan = doctor; Loo = North India.
- Cirrus = high and wispy; Cumulonimbus = thunderstorm.
Quick Tips
- Learn the layers in order with their key feature.
- Learn the local winds with their regions.
- Remember the Coriolis rule for the direction of winds.
- Learn the names of cyclones in different regions.
Quick Revision Points
- Troposphere has the weather; stratosphere has ozone.
- Nitrogen is 78% of the air; oxygen is 21%.
- Trade winds blow towards the equator.
- Chinook is the snow-eater of the Rockies.
- Hurricane, typhoon and cyclone are regional names.
Practice Questions With Answers
- In which layer of the atmosphere does the weather occur?
Answer: Troposphere - In which layer is the ozone layer found?
Answer: Stratosphere - Which gas is the most abundant in the atmosphere?
Answer: Nitrogen - Which wind is called the snow-eater?
Answer: Chinook - What is the instrument for measuring wind speed?
Answer: Anemometer - What is the rainfall caused by the mountains called?
Answer: Orographic rainfall - What are tropical cyclones called in the Atlantic?
Answer: Hurricanes - Which belt is called the doldrums?
Answer: Equatorial low pressure belt - Which wind is hot and dry in North India?
Answer: Loo - Which cloud brings thunderstorms?
Answer: Cumulonimbus
How to Practise This Chapter
Practise 10 questions every day and write the steps on paper. Then attempt timed sets from our practice papers and the previous year papers page. See all topics on the Indian Geography notes page, read the previous topic Earth Interior, Rocks and Landforms and the next topic Energy Resources of India.
Frequently Asked Questions
What are the layers of the atmosphere?
Troposphere, stratosphere, mesosphere, thermosphere and exosphere.
Where is the ozone layer?
In the stratosphere, between about 15 and 35 km.
Which gas forms the most part of the air?
Nitrogen, with 78%.
What are the trade winds?
Steady winds blowing from the subtropical highs towards the equator.
What are the Roaring Forties?
The strong westerly winds in the southern hemisphere around 40° S.
What is the Coriolis force?
The force due to the rotation of the earth that deflects winds to the right in the north and to the left in the south.
What is the Loo?
A hot and dry local wind of North India in summer.
What are the types of rainfall?
Convectional, orographic and cyclonic.
What is the eye of a cyclone?
The calm low-pressure centre of the cyclone.
What is an anemometer?
An instrument to measure wind speed.
Is this topic asked in SSC?
Yes. Climatology is a regular topic in the geography part.
What is a rain shadow area?
The dry leeward side of a mountain.
Previous chapter
Earth Interior, Rocks, Earthquakes, Volcanoes and Landforms: Physical Geography Notes for SSC Exams
Next chapter
Energy Resources of India: Coal, Petroleum, Natural Gas, Hydro, Nuclear and Renewable Energy with Locations for SSC
Rahul Kumar
SSC Exam Expert & Content Editor
Rahul is a senior SSC exam strategist with 8+ years of experience helping aspirants crack CGL, CHSL and MTS exams. He writes in-depth notification breakdowns, exam pattern guides and preparation strategies.