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🌦️ CIE IGCSE Geography: Weather (Comprehensive Notes)

1. 🌍 Key Definitions

  • Weather: The day-to-day condition of the atmosphere (e.g. temperature, rainfall, wind).
  • Climate: The average weather conditions over a long period (usually 30+ years).
  • Meteorology: The study of weather.

2. 🌡️ Elements of Weather

You must know these main elements:

  • Temperature
  • Rainfall (precipitation)
  • Humidity
  • Wind speed
  • Wind direction
  • Air pressure
  • Sunshine
  • Cloud cover

3. 📊 Weather Instruments & Data Collection

🔹 Stevenson Screen​

✅ Description​

  • A white wooden box with louvered (slatted) sides
  • Raised about 1.25 m above ground
  • Located in an open area, away from buildings/trees

🎯 Purpose​

  • Protects instruments from:
    • Direct sunlight
    • Rain
    • Heat from ground

📌 Why white?​

  • Reflects heat → keeps temperature readings accurate

🔹 Instruments Inside the Stevenson Screen​

🌡️ Maximum-Minimum Thermometer​

  • Measures highest and lowest temperatures in a day
  • Units: °C

💧 Wet and Dry Bulb Thermometer (Hygrometer)​

  • Dry bulb: normal temperature
  • Wet bulb: covered in wet cloth

How it works:​

  • Evaporation cools wet bulb → lower reading
  • Difference gives humidity

Key idea:​

  • Large difference → low humidity (dry air)
  • Small difference → high humidity (moist air)

🔹 Instruments Outside the Stevenson Screen​

🌧️ Rain Gauge​

  • Measures rainfall (mm)
  • Placed:
    • On open ground
    • Away from obstacles
    • Slightly sunk into ground

🌬️ Anemometer​

  • Measures wind speed
  • Units: km/h or m/s

🧭 Wind Vane​

  • Shows wind direction
  • Points to where wind is coming from

☀️ Sunshine Recorder​

  • Uses glass sphere to focus sunlight onto card
  • Burns a trace → measures hours of sunshine

📉 Barometer​

  • Measures air pressure
  • Units: millibars (mb) or hectopascals (hPa)

🔹 Modern Digital Instruments​

  • Automatic weather stations
  • Use sensors to record:
    • Temperature
    • Wind
    • Rainfall
  • Provide continuous data

4. ☁️ Cloud Observation

🔹 Types of Clouds​

Cloud TypeHeightAppearanceWeather
CirrusHighThin, wispyFair weather
CumulusMediumFluffy, whiteDry, sunny
StratusLowGrey layerOvercast
Nimbus (Cumulonimbus)Low–highTall, darkHeavy rain, storms

🔹 Cloud Cover Measurement​

  • Measured in oktas (0–8)
    • 0 = clear sky
    • 8 = fully covered

5. 🧮 Calculations (Very Important for Exams)

🔹 Mean Daily Temperature​

🔹 Temperature Range​

🔹 Total Rainfall​

  • Add daily rainfall values

🔹 Mean Monthly Rainfall​

🔹 Humidity (Using Wet & Dry Bulb)​

  • Use tables (given in exam)
  • Find difference → match to humidity %

6. 📈 Graphs and Climate Data

🔹 Types of Graphs​

1. Climate Graph​

  • Bar chart → rainfall
  • Line graph → temperature

2. Line Graphs​

  • Show changes over time (e.g. temperature)

3. Bar Charts​

  • Show rainfall or sunshine

🔹 Interpreting Climate Graphs​

Look for:​

  • Wettest month
  • Driest month
  • Temperature range
  • Seasonal patterns

🔹 Example Patterns​

  • Equatorial climate: High rainfall all year
  • Desert climate: Very low rainfall
  • Temperate climate: Seasonal variation

7. 📍 Siting of Instruments (Exam Favourite)

🔹 Key Rules​

  • Open area (no buildings/trees)
  • Level ground
  • Away from artificial heat
  • Grass surface (not concrete)

🔹 Why?​

  • To ensure accurate and reliable data

8. ⚠️ Common Errors in Data Collection

  • Rain gauge near buildings → inaccurate rainfall
  • Thermometer in sunlight → too hot
  • Wind instruments too low → reduced readings

9. 🧠 Exam Tips

🔑 Definitions You Must Know​

  • Weather vs climate
  • Humidity
  • Air pressure
  • Precipitation

🔑 Common Questions​

1. “Describe how data is collected”​

👉 Mention:

  • Instruments
  • Measurements
  • Units

2. “Explain the siting of a Stevenson Screen”​

👉 Include:

  • Height
  • Open space
  • White colour
  • Louvered sides

3. “Calculate…”​

👉 Show working clearly!

4. “Describe a graph”​

👉 Do NOT explain — just describe patterns:

  • “Temperature increases from…”
  • “Rainfall peaks in…”

🔑 Command Words​

  • Describe = say what you see
  • Explain = give reasons (use because)
  • Calculate = show working

10. 🌍 Real-Life Example

Weather Station (e.g. airports)​

  • Airports like Heathrow Airport use weather stations to:
    • Track wind speed/direction
    • Ensure safe take-offs and landings

11. 📝 Quick Revision Summary

  • Weather is short-term, climate is long-term
  • Stevenson Screen protects instruments
  • Know ALL instruments + functions
  • Practice calculations + graph interpretation
  • Always include units in answers