Weather Instruments IGCSE Geography
Temperature Max Min Thermometer Six’s Thermometer Max-Mercury Min-Alcohol Measures shade temperature (Stevenson’s screen) Read off at bottom of the index (reset with magnet) Read at eye level Measured in ºC
Humidity Wet/Dry Bulb thermometer Hygrometer Comparison tables Wick and reservoir of water Comparison tables Calculate depression of wet bulb (Dry – Wet) Read off table Measures in shade (Stevenson’s screen) Units = % Relative humidity
Wind Speed Anemometer Km per hour Cups or blades Clear unobstructed location Km per hour
Wind Direction Wind Vane Recorded on Wind Rose Compass Directions
Air Pressure Aneoid Barometer Barograph Millibars Plots changes in pressure Millibars Measured in shade (Stevenson’s screen)
Rainfall Rain gauge Siting factors Regular intervals (24hours) Clear view of sky Recessed into ground Approx 30cm above ground Grassy surface (avoid splash back) Read off at eye level Regular intervals (24hours)
Sunshine Sunshine recorder Glass ball focuses light Burns a timeline Traces sun shine not hours of daylight Glass ball focuses light Burns line onto card Units = Hours
Stevenson’s Screen Houses temperature / humidity /pressure instruments Features Insulated roof Painted white to reflect heat Louvered (slatted) sides aid air circulation Located 1.25-2m above ground
Cloud Cover Cloud Mirror Divide mirror into 16 equal squares Lay mirror on ground with clear view of sky Estimate cover Units = Oktas