Class 7 | SST
Chapter 2 | Understanding the Weather
Aligned with CBSE | NCERT | School & Olympiad Standards
Focus on What Matters Most
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Weather vs Climate
- Weather is the state of the atmosphere at a particular time & place — it changes hour to hour.
- Climate is the long-term average of weather over 30+ years for a region.
- The Troposphere (6–18 km thick) is the lowest atmospheric layer, where nearly all weather occurs.
- Weather stations measure and track data — temperature, pressure, wind, humidity — at regular intervals.
- The IMD (India Meteorological Department), established in 1875, is India's nodal forecasting agency.
The 5 Elements of Weather
- Temperature — the degree of hotness or coldness of the air.
- Precipitation — water falling from the sky: rain, snow, sleet, or hail.
- Atmospheric Pressure — the weight of the air above and around us.
- Wind — air moving from high-pressure to low-pressure areas.
- Humidity — the amount of water vapour present in the air.
IMD est. 1875
Troposphere
IMD Motto
"ādityāt jāyate vriṣhti" — "From the sun arises rain." The sun's heat drives the entire weather cycle: evaporation, humidity, and precipitation.
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Quick Recall — Sprint Facts
Sea Level Pressure~1013 millibars (mb)
Depression ZoneBelow 1000 mb — signals storm
Temperature RangeMax − Min (over 24 hrs)
Mean Daily Temp(Max + Min) ÷ 2
Dry Humidity20–40% relative humidity
Humid Weather60–80% relative humidity
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Key Terms
🔑 Relative Humidity
Water vapour in air compared to the max it can hold at that temperature.
🔑 Sleet & Hail
Sleet is frozen/partly frozen rain; hail is small, hard balls of ice.
🔑 Loo
Strong, hot, dusty winds blowing across North India in summer.
🔑 Meteorology
The systematic study of weather and how it evolves.
Olympiad & Challenger
🏆 Coriolis Effect
Earth's rotation makes cyclones spin anticlockwise in the Northern Hemisphere, clockwise in the Southern.
🏆 Mission Mausam
India's 2024 initiative scaling Doppler Weather Radars from 14 to 100 for sharper local forecasts.
🏆 Wet-Bulb Temperature
A survivability threshold (35°C) measuring the body's ability to cool itself by sweating.
🏆 Urban Heat Island
Cities run 2–5°C warmer than nearby rural areas due to concrete and lack of vegetation.
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Wind Vane vs Anemometer
A Wind Vane shows direction (a pointer); an Anemometer measures speed (rotating cups). Don't mix the two up.
Pressure Acts in All Directions
Air pressure isn't just downward — it pushes equally in every direction, including sideways and upward.
Altitude & Oxygen
As altitude increases, both atmospheric pressure and oxygen levels decrease — this is why climbers feel breathless at height.
Falling Barometer = Storm
A rapidly falling barometer reading signals an approaching storm, never fair weather — a commonly reversed fact.
Aviation Wind Socks
Pilots check wind socks on runways to judge wind direction before safe takeoff and landing.
Agriculture Planning
Farmers use weather forecasts to time sowing and harvesting around expected rain.
Disaster Management Alerts
Colour-coded alerts (Yellow/Orange/Red) help authorities evacuate coastal areas ahead of cyclones.
Household Weather Clues
Coconut oil turning solid in winter is a simple everyday sign of falling temperature — no thermometer needed.
Always Include Units
Rainfall in "mm", pressure in "mb", temperature in "°C/°F" — answers without units lose marks.
Rain Gauge Diagram
The collecting funnel must be drawn wider than the measuring cylinder — a common labelling slip.
Wind Definition Upgrade
"Moving air" alone is a Class 6 answer. In Class 7, state that wind moves from high-pressure to low-pressure areas.
Weather ≠ Climate on Paper
Using "weather" and "climate" interchangeably in a definition-based question is a frequent mark-loss trap — always distinguish the timeframe.
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Logic Chain
Step 1
The sun heats an area of land or sea unevenly.
Step 2
Heated air expands and rises, creating a zone of low pressure below.
Step 3
Cooler, high-pressure air from surrounding areas rushes in to fill the gap.
Step 4
This moving air is wind — and if the pressure drop is sharp enough, it becomes a storm.
🦉
Mentor Byte
Don't just memorize the instrument table. Become a "Junior Meteorologist" for a week — track local weather warnings on the Mausam or Damini app. Once you watch a "Yellow Watch" turn into an "Orange Alert" in real life, the pressure-wind concepts will click forever.
Parent Tip
Ask your child to check today's IMD forecast together and predict tomorrow's weather before checking again — this builds real observational habit, not just rote memory.