2. Understanding the Weather

Leave a Comment / Uncategorized

Chapter 2: Understanding the Weather 🌦️

Grade 7 • Exploring Society: India & Beyond Theme: India and the World — Land & People
“A change in the weather is sufficient to create the world and oneself anew.” — Marcel Proust
Quick Navigation:

🧠 The Big Questions

  1. How can we measure and monitor the weather around us?
  2. How do weather predictions help us prepare for heavy rain, storms, droughts, and heat waves?

🌍 What is Weather?

  • Weather = state of the Earth’s atmosphere at a particular time and place.
  • Atmosphere = layer of gases (air) surrounding Earth. Think of it like a multi-layered cake.
  • Troposphere (lowest layer): where humans, animals, and plants live and almost all weather happens.
    • Extends ~6–18 km above ground: thinner at poles (cold air contracts), thicker in tropics (warm air expands).
Let’s Explore: What words do you use (in your language) for weather? Hot, cold, warm, chilly, crisp, humid, windy, pleasant…

🧩 Elements of Weather

  • Temperature how hot or cold the air is.
  • Precipitation rain, snow, sleet, hail that falls from clouds.
  • Atmospheric Pressure weight of the air above us.
  • Wind movement of air; described by speed & direction.
  • Humidity water vapour present in the air.
📚 Glossary chips

Sleet frozen/partly frozen rain • Hail small hard balls of ice • Water vapour water in gaseous form • Forecast to predict in advance • Meteorology study of weather & its evolution.

Think about it: Krishnan in Chennai feels “chilly” after rain; Amir in Kashmir asks “how cold?”. We need standard measurements to compare!
Let’s Explore: Why else should we measure weather precisely? (Planning travel, farming, school trips, disaster readiness, flights, outdoor events…)

🍃 Observing Nature’s Clues

  • Traditional forecasting: birds flying low, ants carrying eggs to higher ground, frogs croaking before rain, pine cones closing in humidity and opening when dry.
  • Communities still use local knowledge to predict the monsoon.
Try this: Ask elders how they predict weather. Collect proverbs/sayings about rain, wind, and seasons in your language.

🌡️ Measuring Temperature

Remember (from Class 6 Science): Clinical vs laboratory thermometers; temperature scales: Celsius (°C) & Fahrenheit (°F). Example: 15°C = 59°F.
  • Types of thermometers: ambient; max–min recorders; increasingly digital for precision & data logging.
  • Useful statistics:
    • Range = Max − Min (usually in 24 h).
    • Mean daily temperature = (Max + Min) ÷ 2.
Everyday science: Snow melts faster when warm; coconut oil solidifies in winter; curd sets slower in cold; cloudy evenings feel cooler.
Don’t Miss Out – IMD: India Meteorological Department (set up 1875) motto: ādityāt jāyate vṛiṣṭi — “From the sun arises rain.”
Why? Solar heat drives evaporation → clouds → rainfall.
🧮 Practice: Weekly Temperatures (Madhya Pradesh)

Use any weekly max–min chart to compute range and mean daily temperature. How would Amir interpret “20°C feels cold in Chennai”?

☔ Measuring Precipitation (Rain/Snow/Sleet/Hail)

  • Rain gauge measures rainfall. Water collected height (in mm) = rainfall received (e.g., 5 mm).
  • Place in open area, level & stable; read at the same time daily. Snow is melted before measuring.
Make & Measure: Build a simple rain gauge. Record daily for a month; compute weekly averages and comment on variations.

🧪 Atmospheric Pressure

  • Pressure of the air around/above us; often sensed as “heaviness” before storms.
  • Higher near sea level; lower at high altitudes → less oxygen for the body → breathless/dizzy/tired.
  • Sometimes drops sharply to form a depression/low-pressure system → can intensify into storms/cyclones.
  • Measured by: Barometer in millibars (mb). Normal at sea level ≈ 1013 mb; below 1000 mb often indicates a depression.
Think about it: Who uses pressure data? (Meteorologists, pilots, sailors, disaster managers, mountaineers, fishermen, farmers…)
High-Altitude Life: Army personnel at Khardung La (~5600 m) work with ~650 mb pressure. Travellers must acclimatise with pauses.

🌬️ Wind: Direction & Speed

  • Wind blows from high pressure → low pressure.
  • It aids seed dispersal, influences flights & sailing, helps farmers anticipate rain direction, and speeds up soil drying.
  • Wind vane (weather vane): shows direction. A fabric version on runways is a wind sock.
  • Anemometer: cups spin faster in stronger wind to measure speed (km/h).
Think about it: What if there were no wind? How would that change seed dispersal and local weather feels?

💧 Humidity

  • Amount of water vapour in air; depends on temperature, wind, pressure, and location (e.g., coastal vs inland).
  • Relative Humidity (RH): 0% (no vapour) → 100% (saturated). Typical: dry 20–40%; humid 60–80%.
  • Evaporation cools surroundings; high RH slows evaporation → clothes dry slowly & we feel sticky.
  • Measured by: Hygrometer (various types). Important in food processing, museums, manufacturing, and weather forecasting.
Kochi vs Jaipur: Which has higher RH? How to compare Kochi vs Mangaluru? (Use hygrometers and RH data.)
Think about it: If Delhi is 52% RH and Kochi 84% (same temperature), where will clothes dry faster? Where will you sweat more?

🏗️ Weather Stations & Automated Weather Stations (AWS)

  • A weather station brings instruments together to take regular readings for mapping and forecasting.
  • AWS = self-operating sensors for temperature, humidity, wind, precipitation, and pressure; used in agriculture, aviation, navigation, environment, etc.
Don’t Miss Out: In 2023, NDMA set up an AWS at a glacial lake in Sikkim (>4800 m) for early information on upcoming weather conditions.

🛰️ Predicting the Weather

  • Meteorologists collect & analyse long-term data to forecast. With climate change, extremes (droughts, floods, cyclones) are more frequent.
  • Accurate forecasts save lives: warn fishermen of storms, evacuate coasts for cyclones, mobilise disaster-response resources.
🗺️ IMD Warning Map (19 May 2024)
  • Colour codes indicate No Warning / Watch (Be Updated) / Alert (Be Prepared) / Warning (Take Action).
  • Icons include: Ground frost, Strong surface winds, Thunder & lightning, Hot & humid, Heat wave, Cold wave/day, Fog, Heavy to Extremely heavy rain/snow, Hailstorm, Dust storm.
  • Explore: Which states had warnings? Which regions were free of severe weather? What caused warnings in Tripura and Lakshadweep on that day?

📌 Before We Move On — Key Takeaways

  • Temperature, humidity, precipitation, wind, pressure together define weather at a place and time.
  • We measure each element with special instruments; data helps us monitor & predict weather.
  • Different elements dominate at different times: rainfall in July, temperature in May/Dec, pressure in cyclones, wind during loo (hot, dusty summer winds in North India) or forest fires.
  • Weather and climate are closely linked — more in the next chapter.

📝 Questions & Activities (from the Chapter)

  1. Match the instrument with the element:
    • (1) Hygrometer
    • (2) Anemometer
    • (3) Barometer
    • (4) Thermometer
    • (5) Rain gauge
    • (a) Precipitation
    • (b) Atmospheric pressure
    • (c) Wind direction & speed
    • (d) Humidity
    • (e) Temperature
  2. Clothing advice: Mumbai in June forecast = 29°C, 84% RH. What should Jyotsna pack?
  3. Set up a rain gauge: Choose the best site: vegetable garden • terrace • open ground with platform • compound wall • verandah. Discuss and justify your choice.
  4. IMD Jammu & Kashmir daily weather (01-02-2024): Write a short weather report script using parameters like max/min temperature, departures, humidity (08:30 & 17:30), rainfall (R/F), snowfall (S/N).
    Tip: Cover the range, where it was warmer/colder than normal (DEP), which stations had rain/snow, and how humid the air felt at morning vs evening.
📋 Example layout for a station-wise table (use with IMD data)
Station Max Temp (ACT/ NOR / DEP) °C Min Temp (ACT/ NOR / DEP) °C Rainfall R/F (mm) Snow S/N (cm) RH 08:30 (%) RH 17:30 (%)
SRINAGAR— / — / —— / — / —————
GULMARG— / — / —— / — / —————
PAHALGAM— / — / —— / — / —————

End of Chapter 2 Notes • Made learner-friendly & mobile-ready 👩‍🎓📱

Chapter 2: Understanding the Weather — Exercises & Answers

Grade 7 • Exploring Society: India & Beyond Fully solved • Mobile-friendly
Quick Navigation:

📘 1) Textbook Exercises — Questions & Model Answers

Q1. Match the instrument with the weather element it measures.

InstrumentCorrect Match
(1) HygrometerHumidity
(2) AnemometerWind direction & speed
(3) BarometerAtmospheric pressure
(4) ThermometerTemperature
(5) Rain gaugePrecipitation (rain/snow after melt)
One-line check: Hygrometer→Humidity • Anemometer→Wind • Barometer→Pressure • Thermometer→Temperature • Rain gauge→Rainfall.

Q2. Jyotsna plans for Mumbai in June (forecast: 29°C & 84% humidity). What should she pack?

Light, breathable cottons/linen; quick-dry T-shirts; airy trousers/skirts; comfortable sandals; a raincoat/compact umbrella (monsoon); waterproof phone pouch; cap; light sunscreen; reusable water bottle & ORS. Avoid heavy denim/synthetics that trap sweat.

Q3. Best site for a rain gauge (choose & justify):

  • 1) School vegetable garden • 2) Terrace • 3) Open ground with elevated platform • 4) Compound wall • 5) Verandah
Option 3 — Open ground with a small raised, level platform: it is away from trees/walls (no splash-in or wind eddies), has open sky view, and the elevation prevents puddle splashback. Terrace/walls/verandah distort readings; garden vegetation obstructs raindrops.

Q4. Using the IMD Jammu & Kashmir daily table (01-02-2024), write a short weather report script.

✅ Model Script (concise, student-friendly)

Good evening! Here’s the Jammu & Kashmir weather round-up for 1 Feb 2024.
Temperatures: Daytime maximums were generally below/near normal across the valley. Srinagar stayed cool; Gulmarg, at high altitude, remained sub-zero through the day. Minimums dipped to freezing or below in several stations such as Pahalgam and Gulmarg.
Moisture & Rain/Snow: Morning humidity was very high (often above 90%) at many stations like Qazigund, Kupwara, and Kukernag, keeping the air damp and cold. Gulmarg reported fresh wintry precipitation (snow) with saturated evening humidity (~100%). Srinagar saw only a trace of rainfall.
Comfort Index: With high humidity and low temperatures, conditions felt colder than the thermometer readings, particularly in the higher reaches. Roads at higher elevations may be slippery; travellers should exercise caution.
Outlook: Cold to very cold nights likely to persist in the upper reaches with a possibility of localized snow; valley areas stay cool and humid.

🔤 2) One-Word Answer Questions (10)

  1. Layer where almost all weather occurs: Troposphere
  2. Instrument to measure rainfall: Rain gauge
  3. Instrument to measure humidity: Hygrometer
  4. Instrument to measure wind speed: Anemometer
  5. Instrument to measure air pressure: Barometer
  6. Normal sea-level pressure (approx.): 1013 mb
  7. Wind blows from ____ pressure to ____ pressure: High; Low
  8. India’s national weather agency: IMD
  9. IMD motto “From the sun arises rain” (Sanskrit): Ādityāt jāyate vṛiṣṭi
  10. AWS expands to: Automated Weather Station

🧩 3) Fill in the Blanks (10)

  1. Weather is the state of the ________ at a particular time and place. atmosphere
  2. Most weather happens in the ________. troposphere
  3. The layer above the troposphere is the ________. stratosphere
  4. Rainfall is commonly measured in ________. millimetres
  5. Air pressure is measured in ________. millibars (mb)
  6. A region of very low pressure is called a ________. depression
  7. Humidity is usually expressed as ________ humidity. relative
  8. The instrument that measures wind speed is an ________. anemometer
  9. IMD was established in the year ________. 1875
  10. The hot, dusty summer wind in North India is called ________. loo

✅ 4) True or False (10) — with Explanations

1) Most weather takes place in the stratosphere.
False — It occurs in the troposphere, the lowest layer of the atmosphere.
2) The troposphere is thinner at the poles than at the equator.
True — Cold air at the poles contracts, making the layer thinner; warm tropical air expands.
3) Air pressure increases with height above sea level.
False — It decreases with altitude; the air gets thinner and oxygen availability drops.
4) Wind blows from low pressure to high pressure.
False — Wind blows from high → low pressure areas.
5) A rain gauge should be placed under a tree to avoid wind.
False — Trees obstruct rain and cause splash errors; choose an open location.
6) High relative humidity slows down evaporation.
True — Air already holds more vapour, so wet clothes dry slowly and we feel sticky.
7) An anemometer measures precipitation.
False — It measures wind speed; precipitation is measured by a rain gauge.
8) IMD’s motto links the sun to rainfall.
True — Solar heating drives evaporation → clouds → rain.
9) A barometer reading well below 1000 mb may indicate a depression.
True — Low pressure systems can intensify into storms or cyclones.
10) Automated Weather Stations need people to take manual readings every hour.
False — AWS are self-operating; sensors record and log data automatically.

✍️ 5) Very Short Answers (10) — 2–3 lines each

  1. What is weather?
    The condition of the atmosphere (temperature, humidity, precipitation, wind, pressure) at a specific time and place.
  2. Name the five basic elements of weather.
    Temperature, precipitation, atmospheric pressure, wind, and humidity.
  3. Why do we need standard measurements?
    They let everyone compare conditions accurately (e.g., Chennai vs Kashmir) and help plan travel, farming, and safety.
  4. Why must travellers acclimatise at high altitudes?
    Air pressure and oxygen levels are lower; the body needs time to adjust to avoid breathlessness and dizziness.
  5. What does a rain gauge measure?
    Depth of rainfall in millimetres; snow is melted before measurement.
  6. Define relative humidity.
    The amount of water vapour in air relative to the maximum it can hold at that temperature (0–100%).
  7. Why do airports use wind socks?
    They show wind direction and approximate speed to aid safe take-off and landing.
  8. How does humidity affect drying clothes?
    High humidity slows evaporation, so clothes dry slowly; low humidity speeds drying.
  9. What is an AWS?
    An Automated Weather Station — a self-operating setup that records multiple weather parameters.
  10. Why are forecasts vital for fishermen?
    They warn of rough seas, strong winds, and cyclones, preventing loss of life and property.

📝 6) Short Answers (10) — 3–4 lines each

  1. Describe the troposphere.
    It’s the lowest atmospheric layer (~6–18 km), thicker over the tropics and thinner at the poles. Almost all weather (clouds, rain, storms) occurs here, and it contains most of the air we breathe.
  2. How does a rain gauge work and where should it be placed?
    Rain falls into a funnel and collects in a cylinder; the water depth (mm) equals rainfall. Place it level on an elevated, open site away from trees/walls to avoid obstruction and splash-in.
  3. Explain max/min temperature, range and mean.
    Thermometers record the day’s highest (max) and lowest (min). Range = max − min; mean daily temperature = (max + min) ÷ 2 — useful for comparing days and places.
  4. Why is air pressure important for forecasting?
    Falling pressure indicates developing lows/depressions that can deepen into storms or cyclones. Tracking pressure helps issue timely alerts and prepare responses.
  5. How are wind speed and direction measured?
    A wind vane (or sock) shows direction. An anemometer’s rotating cups spin faster in stronger winds; the meter converts rotations to km/h.
  6. Why does high humidity feel “sticky” and slow drying?
    Evaporation causes cooling, but when RH is high, evaporation slows. Sweat lingers, clothes dry slowly, and we feel hot and sticky.
  7. What does an Automated Weather Station (AWS) record and why is it useful?
    It logs temperature, humidity, wind, rainfall, and pressure automatically. Data supports agriculture, aviation, disaster management, and environmental monitoring.
  8. Give clothing/health advice for Mumbai in June (29°C, 84% RH).
    Wear light, breathable clothes; carry a raincoat/umbrella; choose quick-dry footwear; stay hydrated (ORS); prefer loose fits; avoid heavy denim/synthetics.
  9. Choose the best rain-gauge site from given options and justify.
    Open ground with an elevated platform. It ensures unobstructed rainfall capture, minimizes turbulence and splash, and keeps the gauge level and stable.
  10. How do forecasts reduce disaster risk?
    By warning about heat waves, heavy rain, strong winds, and cyclones, authorities can evacuate coasts, halt fishing, pre-position relief, and protect infrastructure — saving lives.

End of Exercises • Chapter 2 • Understanding the Weather • Ready to revise & score high! 🌟

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top

Review My Order

0

Subtotal

Taxes & shipping calculated at checkout

Checkout