Geography

THEME 1: CLIMATOLOGY

1.1 WEATHER

Definition of Key Terms
  • Climatology:
    • The study of weather and climate.
  • Weather:
    • The conditions of the atmosphere at a particular place over a short period of time.
  • Climate:
    • The conditions of the atmosphere at a particular place over a long period of time.
Weather Elements and Measurement

The following are key weather elements, the instruments used to measure them, and the respective units:

1. Temperature
  • Measuring Instrument: Thermometer
  • Measurement Units: Minimum and Maximum in °C
    • How to Measure: Read off measurements directly underneath the metal index.
2. Rainfall
  • Measuring Instrument: Rain Gauge
  • Measurement Units: mm (millimeters)
    • How to Measure: Take readings from the side of the gauge where the water level is horizontal with measurement readings.
3. Wind Direction
  • Measuring Instruments: Wind vane, Wind sock
  • Measurement Method: Compass directions
    • How to Measure: The wind vane points into the direction from which the wind is blowing.
4. Wind Speed
  • Measuring Instrument: Cup anemometer
  • Measurement Units: Knots
    • How to Measure: Take readings off a dial below the cups. The faster the cups rotate, the faster the wind is blowing or speed.
5. Humidity
  • Measuring Instruments: Wet and dry bulb thermometer, Hygrometer
  • Measurement Units: %
    • How to Measure: Take readings where mercury ends on both wet and dry bulb thermometer. The unit is in °C, but a hygrometer table is used to convert to %.
6. Sunshine
  • Measuring Instrument: Sunshine recorder
  • Measurement Units: Hours per day
    • How to Measure: Sunrays are focused on a piece of paper marked hours of the day through a glass ball. Focused rays burn a line which shows the hours of sunshine. If a cloud covers the sun, there will not be rays to burn a line. The number of hours the rays have burned is then counted.
7. Air Pressure
  • Measuring Instruments: Aneroid barometer, Barograph
  • Measurement Units: Mbar (Millibars), hPa (hectopascals)
    • How to Measure: Take readings of a dial in the aneroid barometer which indicates the amount of pressure in air by contraction and expansion of the cylindrical drum of the barometer.