Chapter 5: Air

🌬️ Complete Chapter for PSTET Paper II (Social Studies)

🎯 Learning Objectives for PSTET Aspirants

After completing this chapter, you will be able to:

Analyze the composition of the atmosphere and the role of each component
Describe the structure of the atmosphere with characteristics of each layer
Distinguish between weather and climate with clear examples
Explain the elements of weather and climate—temperature, air pressure, winds, and moisture
Understand the monsoon system and its significance for India and Punjab
Apply pedagogical strategies through experiments, models, and weather diaries

5.1 Composition of the Atmosphere: Gases, Dust Particles, and Water Vapor

🌍 What is the Atmosphere?

The atmosphere is the thin blanket of air that surrounds the Earth. It extends outward to about 1,000 kilometers where it gradually transitions to interplanetary space. This gaseous envelope is held by Earth's gravitational force and rotates with the Earth .

🧪 Gaseous Composition

The atmosphere is a mixture of several gases. The table below shows the permanent gases that make up the bulk of dry air:

Gas	Percentage by Volume	Role and Importance
Nitrogen (N₂)	78.08%	Essential for plant growth; dilutes oxygen; forms proteins
Oxygen (O₂)	20.95%	Required for respiration (breathing); supports combustion
Argon (Ar)	0.93%	Inert gas; no significant role in weather
Carbon Dioxide (CO₂)	0.04% (variable)	Greenhouse gas; traps heat; essential for photosynthesis
Neon (Ne)	0.0018%	Trace gas; no significant role
Helium (He)	0.0005%	Trace gas; no significant role
Methane (CH₄)	0.0002%	Greenhouse gas
Ozone (O₃)	Variable	Absorbs harmful UV radiation; present in stratosphere
Hydrogen (H)	0.00005%	Trace gas

💡 Key Insight: The two most abundant gases—nitrogen and oxygen—together constitute about 99% of the total volume of dry air.

💧 Water Vapor: The Variable Component

Water vapor is the most variable component of the atmosphere. Its concentration ranges from 0% to 4% depending on:

Factor	Influence
Temperature	Warm air can hold more water vapor than cold air
Location	Tropical regions have higher humidity; deserts have very low humidity
Altitude	Water vapor decreases with increasing altitude
Time of day	Humidity typically higher at night and early morning

Importance of Water Vapor:

Source of all precipitation (rain, snow, hail)
Absorbs and releases latent heat—drives weather systems
Creates greenhouse effect—traps heat in the atmosphere
Determines humidity and comfort levels

🌫️ Dust Particles and Aerosols

Dust particles, smoke, salt crystals, and other solid particles are present in varying amounts:

Source of Particles	Examples
Natural	Soil dust, sea salt, volcanic ash, pollen, forest fire smoke
Anthropogenic	Industrial emissions, vehicle exhaust, agricultural burning

Importance of Dust Particles:

Act as hygroscopic nuclei—water vapor condenses around them to form clouds
Absorb and scatter solar radiation
Contribute to air pollution in urban areas
Influence visibility (haze, smog)

📝 PSTET Focus Point: Water vapor and dust particles are the most variable components and are crucial for cloud formation and weather phenomena.

5.2 Structure of the Atmosphere: Layers and Their Characteristics

📊 The Five Atmospheric Layers

Based on temperature variation with altitude, the atmosphere is divided into five distinct layers :

   Altitude (km)
        ↑
    1000│┌────────────────────────────────────┐
        ││           EXOSPHERE                │
        ││   (Transition to space)            │
    600 │└────────────────────────────────────┘
        │┌────────────────────────────────────┐
        ││         THERMOSPHERE               │
        ││   Temperature ↑ with altitude      │
    85  ││   Includes Ionosphere              │
        │└────────────────────────────────────┘
        │┌────────────────────────────────────┐
        ││         MESOSPHERE                 │
    50  ││   Temperature ↓ with altitude      │
        ││   Meteors burn up here             │
        │└────────────────────────────────────┘
        │┌────────────────────────────────────┐
        ││        STRATOSPHERE                │
    12  ││   Temperature ↑ with altitude      │
        ││   Ozone layer (20-30 km)           │
        │└────────────────────────────────────┘
        │┌────────────────────────────────────┐
        ││        TROPOSPHERE                 │
     0  ││   Temperature ↓ with altitude      │
        ││   Weather phenomena occur here     │
        ││   Contains 99% of water vapor      │
        └┴────────────────────────────────────┴──► Temp.

Layer 1: Troposphere

Feature	Description
Altitude Range	0-12 km (8 km at poles; 16 km at equator)
Temperature Trend	Decreases with altitude (~6.5°C per km)
Thickness	Thinnest at poles; thickest at equator
Contains	75% of atmospheric mass; 99% of water vapor
Key Phenomena	All weather occurs here—clouds, rain, storms, fog
Boundary	Tropopause—temperature becomes constant

Significance: The troposphere is the "weather sphere" where all life exists. The constant mixing of air (convection) gives it its name—from Greek tropos meaning "turning" or "mixing" .

Layer 2: Stratosphere

Feature	Description
Altitude Range	12-50 km
Temperature Trend	Increases with altitude (up to 0°C at top)
Ozone Layer	20-30 km altitude—absorbs 95% of UV radiation
Characteristics	Very stable; no convection; jet streams at lower levels
Boundary	Stratopause

Significance: The ozone layer protects life on Earth from harmful ultraviolet radiation. The stable conditions make this layer ideal for aircraft flight .

Ozone Formation:

O₂ + UV radiation → 2O (oxygen atoms)
O + O₂ → O₃ (ozone)
O₃ + UV radiation → O₂ + O (continuous cycle)

Layer 3: Mesosphere

Feature	Description
Altitude Range	50-85 km
Temperature Trend	Decreases with altitude (to -90°C at top)
Characteristics	Coldest layer of the atmosphere
Phenomena	Meteors burn up here due to friction
Boundary	Mesopause

Significance: The mesosphere is Earth's "meteor shield" —countless meteors disintegrate here before reaching the surface. It is also where noctilucent clouds (night-shining clouds) form.

Layer 4: Thermosphere

Feature	Description
Altitude Range	85-600 km
Temperature Trend	Increases with altitude (up to 1500°C or more)
Ionosphere	Lower region (to 550 km)—gases are ionized
Phenomena	Aurora borealis (Northern Lights); reflects radio waves
Characteristics	Air is extremely thin; temperature is high but "heat" is not felt

Significance: The ionosphere enables long-distance radio communication by reflecting radio waves back to Earth. The beautiful auroras occur when charged solar particles interact with ionized gases.

Layer 5: Exosphere

Feature	Description
Altitude Range	600-1000+ km
Temperature Trend	Constant; very high
Composition	Hydrogen and helium atoms extremely sparse
Characteristics	Transition to interplanetary space; atoms can escape Earth's gravity
Phenomena	Satellites orbit in this region

Significance: The exosphere is the outermost layer where Earth's atmosphere gradually fades into the vacuum of space.

📝 PSTET Focus Point: Remember the temperature trend in each layer:
Troposphere: ↓ decreases
Stratosphere: ↑ increases
Mesosphere: ↓ decreases
Thermosphere: ↑ increases
Exosphere: constant

5.3 Weather and Climate: Distinction Between the Two Terms

🌤️ What is Weather?

Weather refers to the day-to-day condition of the atmosphere at a particular place and time. It includes short-term changes in temperature, humidity, precipitation, cloud cover, wind speed, and wind direction.

Aspect	Weather
Time Scale	Hours to days
Variability	Highly variable; can change rapidly
Study	Meteorology
Examples	"Today is sunny and 35°C"; "It rained heavily yesterday"

🌦️ What is Climate?

Climate is the long-term average of weather conditions over a large area, measured over at least 30 years. It represents the typical weather patterns and their variability.

Aspect	Climate
Time Scale	Decades to centuries
Variability	Relatively stable; changes slowly
Study	Climatology
Examples	"Punjab has a continental climate with hot summers and cool winters"

🔍 Comparison: Weather vs. Climate

Feature	Weather	Climate
Duration	Short-term (hours to days)	Long-term (30+ years)
Components	Current conditions	Statistical averages
Predictability	Difficult beyond a week	More predictable patterns
Change	Rapid and frequent	Slow and gradual
Scope	Local	Regional to global
Analogy	Your mood today	Your personality

💡 Simple Analogy for Teaching

Weather is what clothes you choose to wear today.
Climate is the entire wardrobe you own.

If it's raining (weather), you grab an umbrella
If you live in a rainy region (climate), you own multiple umbrellas and raincoats

📊 Examples for PSTET

Statement	Weather or Climate?	Reason
"The temperature in Ludhiana today is 28°C"	Weather	Specific place, specific time
"Punjab experiences very hot summers"	Climate	Generalization over many years
"Monsoon arrived in Kerala on June 1st"	Weather	Specific event
"India has a tropical monsoon climate"	Climate	Long-term pattern

5.4 Elements of Weather and Climate

5.4.1 Temperature: Factors Affecting Temperature

Temperature is the measure of heat present in the atmosphere. It is the most important element of weather and climate.

☀️ Insolation

Insolation (Incoming Solar Radiation) is the solar energy that reaches the Earth's surface. It is the primary source of heat for the atmosphere .

Factor Affecting Insolation	Explanation
Sun's angle/altitude	Higher angle = more concentrated energy
Duration of daylight	Longer days = more insolation received
Atmospheric path length	Lower angle = longer path = more absorption/scattering

🌍 Latitude

Temperature decreases from the equator toward the poles due to :

Latitude Effect	Reason
Equator (0°)	Sun's rays are almost vertical; concentrated energy; shortest atmospheric path
Mid-latitudes (30°-60°)	Rays are slanting; energy spread over larger area
Poles (90°)	Rays are very slanting; longest atmospheric path; high reflection (albedo) from snow/ice

Temperature Gradient: Approximately 1°C decrease for every degree of latitude away from equator.

🏔️ Altitude

Temperature decreases with increasing altitude in the troposphere .

Altitude Effect	Rate
Normal Lapse Rate	6.5°C per 1,000 meters (approx. 1°C per 165 meters)
Reason	Air is thinner at higher altitudes; fewer molecules to absorb and retain heat

Examples:

Darjeeling (2,045 m) is cooler than Kolkata (9 m)
Mussoorie (2,000 m) is cooler than Dehradun (450 m)

🌊 Distance from Sea (Continentality)

Water heats and cools more slowly than land. This creates temperature differences between coastal and inland areas .

Season	Coastal Areas	Inland Areas
Summer	Cooler (sea breeze moderates temperature)	Hotter (land heats quickly)
Winter	Milder (sea retains heat)	Colder (land cools quickly)

Range of Temperature:

Coastal: Small diurnal and annual range (e.g., Mumbai: 25°C-32°C year-round)
Inland: Large diurnal and annual range (e.g., Delhi: 5°C-45°C)

Other Factors

Factor	Influence on Temperature
Ocean Currents	Warm currents raise temperatures (e.g., Gulf Stream warms NW Europe); cold currents lower temperatures
Prevailing Winds	Winds from warmer regions raise temperatures; from colder regions lower temperatures
Cloud Cover	Clouds reduce daytime heating and nighttime cooling—narrower temperature range
Slope/Aspect	South-facing slopes in Northern Hemisphere are warmer

5.4.2 Air Pressure: Pressure Belts and Factors

Air pressure is the weight of the air column above a point. It is measured in millibars (mb) or hectopascals (hPa).

🌐 Global Pressure Belts

On Earth's surface, there are seven pressure belts arranged parallel to latitudes :

                    NORTH POLE (90°N)
                         │
              POLAR HIGH (90°N)
                         │
              SUB-POLAR LOW (60°N-70°N)
                         │
          SUBTROPICAL HIGH (30°N-35°N)  ← Horse Latitudes
                         │
            EQUATORIAL LOW (0°-5°N/S)   ← Doldrums
                         │
          SUBTROPICAL HIGH (30°S-35°S)  ← Horse Latitudes
                         │
              SUB-POLAR LOW (60°S-70°S)
                         │
              POLAR HIGH (90°S)
                         │
                    SOUTH POLE (90°S)

Pressure Belt	Location	Characteristics
Equatorial Low	0°-5° N and S	Intense heating; air rises; calm winds (Doldrums)
Subtropical High	30°-35° N and S	Descending air; calm winds; major deserts (Horse Latitudes)
Sub-polar Low	60°-70° N and S	Warm and cold air meet; ascending air; stormy
Polar High	90° N and S	Extreme cold; dense air sinks; ice caps

📈 Factors Affecting Air Pressure

Factor	Effect on Pressure	Explanation
Temperature	Warm air → Low pressure Cold air → High pressure	Warm air expands and rises; cold air contracts and sinks
Altitude	Higher altitude → Lower pressure	Thinner air column above
Water Vapor	More vapor → Lower pressure	Water vapor is lighter than dry air
Earth's Rotation	Creates pressure belts	Coriolis effect organizes circulation

🔄 Seasonal Shifting of Pressure Belts

Pressure belts shift with the apparent movement of the Sun :

Season	Shift	Reason
June (Summer Solstice)	5° northward	Sun overhead at Tropic of Cancer (23.5°N)
December (Winter Solstice)	5° southward	Sun overhead at Tropic of Capricorn (23.5°S)
March/September (Equinoxes)	Balanced	Sun overhead at Equator

Significance: This shifting creates seasonal wind patterns, including the monsoon .

5.4.3 Winds: Types and Characteristics

Wind is air moving from high-pressure areas to low-pressure areas. Winds are classified into three main types .

📊 Classification of Winds

                    ┌──────────────────┐
                    │      WINDS       │
                    └────────┬─────────┘
                             │
        ┌────────────────────┼────────────────────┐
        ▼                    ▼                    ▼
┌───────────────┐    ┌───────────────┐    ┌───────────────┐
│   PERMANENT   │    │   SEASONAL    │    │    LOCAL      │
│   (Planetary) │    │  (Secondary)  │    │   (Tertiary)  │
├───────────────┤    ├───────────────┤    ├───────────────┤
│ • Trade Winds │    │ • Monsoons    │    │ • Loo         │
│ • Westerlies  │    │               │    │ • Mistral     │
│ • Polar       │    │               │    │ • Foehn       │
│   Easterlies  │    │               │    │ • Chinook     │
└───────────────┘    └───────────────┘    └───────────────┘

🌬️ Permanent (Planetary) Winds

These winds blow consistently throughout the year from high-pressure belts to low-pressure belts .

Wind Type	Belt	Direction (N. Hem)	Direction (S. Hem)	Characteristics
Trade Winds	30°-0°	Northeast	Southeast	Steady; bring rainfall to east coasts
Westerlies	30°-60°	Southwest	Northwest	Variable; bring weather systems
Polar Easterlies	90°-60°	Northeast	Southeast	Cold, dry; weak and irregular

Roaring Forties: In Southern Hemisphere, between 40°-50°S, westerlies blow with great strength over open ocean, creating stormy conditions .

🍃 Seasonal Winds: The Monsoon

Monsoon refers to the seasonal reversal of wind direction. It is the most important seasonal wind system for India .

Formation of Indian Monsoon

Factor	Role in Monsoon
Uneven Heating	Land heats faster than ocean in summer—creates low pressure over NW India
Shift of Pressure Belts	ITCZ shifts northward over Indian subcontinent
Himalayan Barrier	Prevents winds from escaping north; forces uplift and rainfall
Jet Streams	Tropical easterly jet stream at 15°N enhances monsoon
El Niño/La Niña	El Niño weakens monsoon; La Niña strengthens it

Southwest Monsoon (June-September)

Feature	Description
Direction	Southwest to northeast
Source	Arabian Sea and Bay of Bengal
Rainfall	75% of India's annual rainfall
Arrival	Kerala by June 1st; covers entire country by mid-July

Two Branches:

Arabian Sea Branch: Hits Western Ghats → heavy rainfall on windward side; rain shadow over Deccan
Bay of Bengal Branch: Moves northward → rainfall in West Bengal, Bangladesh, Northeast India; deflects westward over Gangetic Plains

Northeast Monsoon (October-December)

Feature	Description
Direction	Northeast to southwest
Source	Land to sea (continental)
Rainfall	Limited; mainly in Tamil Nadu and coastal Andhra
Nature	Retreating monsoon; associated with cyclones in Bay of Bengal

Importance of Monsoon for India and Punjab

Sector	Importance
Agriculture	60% of cropped area depends on monsoon; kharif crops (rice, cotton, sugarcane)
Water Resources	Replenishes reservoirs, groundwater, and rivers
Economy	Good monsoon → higher agricultural output → rural demand → economic growth
Culture	Festivals (Teej, Onam) celebrate monsoon arrival

For Punjab Specifically:

Monsoon is critical for kharif crops, especially paddy (rice)
Delayed or deficient monsoon affects canal and groundwater supplies
Excess rainfall can cause waterlogging and flooding
The Himalayas create a rain shadow effect, making parts of Punjab relatively drier than areas like Himachal Pradesh

🌬️ Local Winds

Local winds blow over small areas due to local temperature and pressure differences .

Local Wind	Region	Characteristics
Loo	Northern India (Punjab, UP, Bihar)	Hot, dry, strong winds in May-June; can cause heatstroke
Mistral	France (Rhone Valley)	Cold, dry, northerly wind; damages crops
Foehn/Föhn	Alps (Europe)	Warm, dry wind descending leeward slopes; melts snow
Chinook	Rocky Mountains (USA/Canada)	Warm, dry "snow-eater" wind
Sirocco	Sahara to Southern Europe	Warm, humid, dusty wind
Harmattan	West Africa	Dry, dusty northeasterly trade wind
Bora	Adriatic coast (Eastern Europe)	Cold, dry, gusty northeasterly

Land and Sea Breezes

Time	Land Temperature	Sea Temperature	Pressure	Wind Direction
Day	Warmer	Cooler	Low over land; high over sea	Sea to land (Sea Breeze)
Night	Cooler	Warmer	High over land; low over sea	Land to sea (Land Breeze)

Mountain and Valley Breezes

Time	Slope Temperature	Valley Temperature	Wind Direction
Day	Slopes warm faster	Cooler air in valley	Valley to slope (Valley Breeze/Anabatic)
Night	Slopes cool faster	Warmer air in valley	Slope to valley (Mountain Wind/Katabatic)

5.4.4 Moisture: Humidity, Clouds, and Precipitation

💧 Humidity

Humidity is the amount of water vapor present in the air .

Type	Definition
Absolute Humidity	Actual mass of water vapor per volume of air (g/m³)
Relative Humidity	Percentage of water vapor air holds relative to maximum it could hold at that temperature
Specific Humidity	Mass of water vapor per mass of air (g/kg)

Relative Humidity is the most commonly used measure:

If RH = 80%, air contains 80% of the water it could hold at that temperature
Warm air can hold more water vapor than cold air

Dew Point: The temperature at which air becomes saturated (100% RH). Further cooling causes condensation .

☁️ Clouds

Clouds form when moist air rises, cools, and water vapor condenses around hygroscopic nuclei (dust, salt, smoke) .

Cloud Classification by Altitude

Level	Altitude	Cloud Types	Characteristics
High Clouds	>6,000 m	Cirrus, Cirrostratus, Cirrocumulus	Ice crystals; thin, white; no precipitation
Middle Clouds	2,000-6,000 m	Altostratus, Altocumulus	Water droplets/ice crystals; may bring light rain
Low Clouds	<2,000 m	Stratus, Stratocumulus, Nimbostratus	Water droplets; overcast; nimbostratus brings steady rain
Vertical Clouds	Base low to top high	Cumulus, Cumulonimbus	Vertical growth; cumulonimbus produces thunderstorms, hail

Cloud Types and Weather Indications:

Cirrus: Fair weather; may indicate approaching storm
Cumulus: Fair weather (if small); can grow into thunderstorms
Cumulonimbus: Thunderstorms, heavy rain, lightning, hail
Stratus: Overcast, drizzle
Nimbostratus: Continuous rain/snow

🌧️ Precipitation

Precipitation is water falling from clouds in liquid or solid form .

Types of Precipitation

Type	Description	Formation
Rain	Liquid water droplets	Temperatures above freezing throughout
Snow	Ice crystals (snowflakes)	Temperatures below freezing throughout
Sleet	Ice pellets	Rain freezes as it falls through cold layer
Hail	Layers of ice	Strong updrafts in cumulonimbus clouds; ice grows in layers
Drizzle	Very fine droplets (<0.5 mm)	Low clouds (stratus)
Freezing Rain	Supercooled liquid	Rain freezes on contact with cold surfaces

Three Types of Rainfall

Type	Process	Characteristics	Location
Convectional Rainfall	Air heated at surface rises; cools; condenses; precipitates	Short duration; heavy intensity; often with thunder	Equatorial regions; summer afternoons
Orographic/Relief Rainfall	Moist air forced up mountain slope; cools; condenses; precipitates	Windward slope gets heavy rain; leeward slope in rain shadow	Western Ghats, Himalayas (windward slopes)
Cyclonic/Frontal Rainfall	Warm and cold air masses meet; warm air rises over cold; cools; condenses	Moderate to heavy rain; associated with fronts	Mid-latitudes; temperate cyclones

Rain Shadow Effect:

Windward side of mountains: Heavy rainfall
Leeward side (rain shadow): Dry conditions
Example: Western Ghats windward side gets 300-400 cm rain; rain shadow Deccan plateau gets 50-70 cm

5.5 Pedagogical Focus: Hands-On Activities for Teaching About Air

🧒 Understanding the Learner (Classes VI-VIII)

Upper primary students:

Learn best through concrete, hands-on experiences
Need to "see" and "do" to understand abstract concepts
Benefit from connecting science to daily life
Enjoy observing and recording phenomena

💨 Simple Experiments to Show Air Pressure

Experiment 1: The Crushing Can

Aspect	Detail
Objective	Demonstrate that air pressure is strong enough to crush a can
Materials	Empty aluminum soda can, stove/heat source, bowl of cold water, tongs
Procedure	1. Put small amount of water in can and heat until steam comes out 2. Using tongs, quickly invert can into cold water 3. Can implodes instantly!
Explanation	Steam pushes air out. When cooled, steam condenses, creating vacuum. Outside air pressure crushes can.

Experiment 2: The Magical Water Glass

Aspect	Detail
Objective	Show that air pressure can hold water in an upside-down glass
Materials	Glass, water, stiff paper/card
Procedure	1. Fill glass completely with water 2. Cover with card, ensuring no air bubble 3. Hold card firmly and invert glass 4. Remove hand—card stays! Water stays!
Explanation	Air pressure pushing up on card is greater than weight of water pushing down.

Experiment 3: Balloon in a Bottle

Aspect	Detail
Objective	Demonstrate that air occupies space
Materials	Plastic bottle, balloon
Procedure	1. Place balloon inside bottle with mouth stretched over bottle opening 2. Try to inflate balloon—it won't inflate! 3. Make a small hole in bottle—balloon inflates easily
Explanation	Air already in bottle prevents balloon from expanding. Hole allows trapped air to escape.

🧭 Making a Wind Vane

Simple Wind Vane Construction

Step	Instructions
Materials Needed	Straw, stiff paper/card, pin, pencil with eraser, compass, markers
Step 1	Cut arrow shapes (pointer and tail) from card
Step 2	Cut slits in straw ends and insert arrow shapes
Step 3	Push pin through center of straw into pencil eraser
Step 4	Ensure straw can rotate freely
Step 5	Mark N, S, E, W on ground or container

How to Use:

Place wind vane in open area away from buildings/trees
Use compass to orient N correctly
Observe which direction arrow points—wind is named from where it comes FROM
North wind → arrow points North → wind blows from North to South

📓 Maintaining a Weather Diary

Weather Diary Format

Date	Time	Temperature	Wind Direction	Wind Speed	Cloud Cover	Precipitation	Special Notes

Cloud Cover Symbols

Symbol	Cloud Cover	Description
○	Clear sky	0-1/8 clouds
◔	Mostly clear	2/8 clouds
◑	Partly cloudy	3-4/8 clouds
◕	Mostly cloudy	5-7/8 clouds
●	Overcast	8/8 clouds

Wind Speed Estimation (Beaufort Scale Adapted)

Force	Description	Observable Effects
0	Calm	Smoke rises vertically
1-2	Light air/breeze	Smoke drifts; leaves rustle
3-4	Gentle/moderate breeze	Leaves and twigs in motion; small flags extend
5-6	Fresh/strong breeze	Small trees sway; wind felt on face
7+	Gale/storm	Whole trees in motion; walking difficult

Sample Weekly Weather Diary Activity

Day	Date	Temp (°C)	Wind Direction	Cloud Cover	Rain (mm)	Observations
Mon
Tue
Wed
Thu
Fri

🌡️ Making Simple Weather Instruments

Simple Rain Gauge

Step	Instructions
Materials	Plastic bottle, scissors, ruler, stones, marker
Step 1	Cut top off bottle (about 1/3 down)
Step 2	Place stones in bottom for stability
Step 3	Invert top portion like funnel into bottom
Step 4	Mark scale in cm/mm on side
Step 5	Place in open area away from trees/buildings

Simple Thermometer Shelter

Purpose	To shield thermometer from direct sun and rain while allowing air circulation
Materials	Wooden box with slatted sides, painted white (reflects sunlight)
Placement	1.5 m above ground, in open area
Usage	Place thermometer inside; read at same time daily

📝 Classroom Activities and Projects

Activity 1: Monsoon Watch (June-September)

Week	Monsoon Progress	Rainfall in Your Area	News Headlines
Week 1
Week 2
Week 3
Week 4

Activity 2: Local Wind Study

Identify local names for winds in your area
Interview elders about traditional weather knowledge
Create a "Local Winds of Punjab" chart
Example: Loo (hot summer winds), Andhi (dust storms before monsoon)

Activity 3: Cloud Watching

Date	Time	Cloud Type	Weather Following

Activity 4: Weather and Agriculture Connection

Connect weather observations to local crops
Track monsoon progress and relate to:
- Sowing of kharif crops (rice, cotton)
- Transplanting of paddy
- Harvesting of rabi crops (wheat)

📝 Chapter Summary: Key Points for PSTET Revision

🔑 Composition of Atmosphere

Component	Percentage	Role
Nitrogen	78.08%	Plant nutrition
Oxygen	20.95%	Respiration, combustion
Argon	0.93%	Inert
CO₂	0.04%	Photosynthesis, greenhouse effect
Water vapor	0-4%	Precipitation, humidity

🔑 Layers of Atmosphere

Layer	Altitude	Temperature	Key Feature
Troposphere	0-12 km	Decreases	Weather occurs
Stratosphere	12-50 km	Increases	Ozone layer
Mesosphere	50-85 km	Decreases	Meteors burn
Thermosphere	85-600 km	Increases	Ionosphere, auroras
Exosphere	600+ km	Constant	Transition to space

🔑 Weather vs. Climate

Weather: Short-term, day-to-day conditions
Climate: Long-term average (30+ years)

🔑 Factors Affecting Temperature

Insolation, Latitude, Altitude, Distance from sea, Ocean currents, Winds, Cloud cover

🔑 Global Pressure Belts

Belt	Location	Characteristic
Equatorial Low	0°-5°	Doldrums (calm)
Subtropical High	30°-35°	Horse latitudes (calm, deserts)
Sub-polar Low	60°-70°	Stormy
Polar High	90°	Ice caps

🔑 Wind Types

Type	Examples
Permanent	Trade winds, Westerlies, Polar easterlies
Seasonal	Monsoons
Local	Loo, Mistral, Foehn, Chinook, Land/sea breezes

🔑 Monsoon in India

Southwest Monsoon (June-Sept): Main rainy season (75% of rainfall)
Northeast Monsoon (Oct-Dec): Limited to Tamil Nadu coast
Importance: Agriculture (60% cropped area), water resources, economy

🔑 Moisture and Precipitation

Relative humidity: % of water vapor air holds
Cloud types: Cirrus, Cumulus, Stratus, Nimbus
Rainfall types: Convectional, Orographic, Cyclonic
Precipitation forms: Rain, snow, sleet, hail

📝 Practice Questions for PSTET Preparation

Multiple Choice Questions

Which gas constitutes the highest percentage in the atmosphere?
a) Oxygen
b) Carbon dioxide
c) Nitrogen
d) Argon
The ozone layer is found in which layer of the atmosphere?
a) Troposphere
b) Stratosphere
c) Mesosphere
d) Thermosphere
The doldrums are associated with which pressure belt?
a) Subtropical high
b) Equatorial low
c) Sub-polar low
d) Polar high
Which of the following is a local wind in northern India?
a) Mistral
b) Chinook
c) Loo
d) Foehn
The Roaring Forties are associated with which winds?
a) Trade winds
b) Westerlies
c) Polar easterlies
d) Monsoon winds
What causes the monsoon in India?
a) Uniform heating of land and sea
b) Seasonal reversal of wind direction
c) Constant high pressure over India
d) Western disturbances only
Which type of rainfall occurs when moist air is forced to rise over mountains?
a) Convectional rainfall
b) Orographic rainfall
c) Cyclonic rainfall
d) Frontal rainfall
The Horse Latitudes are located at approximately:
a) 0°-5° latitude
b) 30°-35° latitude
c) 60°-70° latitude
d) 90° latitude
What happens to temperature as altitude increases in the troposphere?
a) Increases
b) Decreases
c) Remains constant
d) First increases then decreases
The southwest monsoon in India occurs during which months?
a) October to December
b) January to March
c) June to September
d) April to May

Short Answer Questions

Differentiate between weather and climate with suitable examples.
Explain any three factors affecting the temperature of a place.
Name and describe the four major pressure belts of the Earth.
What are the three types of winds? Give two examples of each.
Describe the process of convectional rainfall with a labeled diagram.

Long Answer Questions

Explain the structure of the atmosphere with reference to its five layers. Describe the characteristics and importance of each layer.
Discuss the mechanism of the Indian monsoon. Why is it important for India, particularly for Punjab?
Describe the three types of rainfall with the help of diagrams and examples from India.
As a teacher, how would you explain the concept of air pressure to Class VI students? Describe any three experiments you would use.
Analyze the role of the Himalayas in influencing India's climate, particularly the monsoon and the rain shadow effect.

✅ Chapter Completion Checklist

Before moving to Chapter 6, ensure you can:

Name the major gases in atmosphere with percentages
Draw and label the five atmospheric layers
Differentiate between weather and climate
Explain factors affecting temperature (at least 4)
Identify all seven pressure belts
Classify winds into three types with examples
Explain monsoon mechanism and importance for India/Punjab
Describe cloud types and their characteristics
Differentiate between three rainfall types
Conduct at least 2 air pressure experiments
Construct a wind vane
Design a weather diary format

🔗 Online Resources for Further Learning

Resource	Description	Link/How to Find
India Meteorological Department	Monsoon updates, weather data	imd.gov.in
NCERT Geography Textbooks	Class VI, VII, VIII resources	ncert.nic.in
NASA Climate Kids	Weather and climate for students	climatekids.nasa.gov
National Geographic Education	Weather resources	education.nationalgeographic.org
Weather Spark	Historical weather data for any location	weatherspark.com
Byjus Geography Articles	Pressure belts, winds, monsoon	byjus.com/free-ias-prep

🎓 Prepared for PSTET Aspirants

This chapter provides comprehensive coverage of "Air" as per PSTET Paper II syllabus. Understanding atmospheric processes is fundamental to geography. Use the experiments and activities to make these concepts come alive for your students. The monsoon section is especially important for the Punjab context—be prepared for questions linking monsoon to local agriculture!

Teacher Eligibility Test

Wednesday, 25 February 2026

Ch 5: Air