Key definitions
Weather — the day-to-day, hour-to-hour changes in our atmosphere.
Climate — the average weather patterns of an area over 30 or more years (limited to temperature and precipitation).
Weather instruments
| Instrument | What it measures / how to read it |
|---|---|
| Anemometer | Wind speed. Electronic reading produced. |
| Barometer | Air pressure. Read the hands of the barometer. |
| Wind vane | Wind direction. The arrow points in the direction the wind is coming FROM. |
| Hygrometer | Humidity. Read the wet bulb and dry bulb readings, then compare the readings to a humidity chart. |
| Maximum and minimum thermometer | Highest and lowest temperature of an area. The left thermometer is minimum, the right thermometer is maximum. |
| Rain gauge | Precipitation. |
Stevenson screen
Stevenson screen — contains various weather instruments to measure the weather.
- Has a roof which prevents rain and direct heat
- Away from buildings, trees and artificial sources of heat
- On level ground
- Painted white to reflect sunlight
- Stands on legs, at least 125 cm from the ground
- Has hinged doors
- Faces away from the sun to avoid direct sunlight
- Sited on grass to make sure there is no excess heat (e.g. from concrete)
- Surrounded by a security fence to avoid damage from animals
- Sides have wooden slats to allow air flow
Clouds
Main types:
- Stratus — greyish and often cover the entire sky. Usually no precipitation (may drizzle).
- Cumulus — puffy and large clouds. Flat base and only around 1000 m above ground. Can develop to form giant cumulonimbus thunder clouds.
- Cirrus — wispy and thin. Very high altitude (6000 m) and usually mean pleasant and fair weather.
Types of clouds:
- Cumulus
- Stratus
- Cirrus
- Cumulonimbus
- Altostratus
- Nimbostratus
Observing cloud cover in the sky
- Estimated using oktas
- Scale of 0 (least cloud coverage) to 8 (most cloud coverage)
- Example: an estimated 4 okta sky is partly cloudy
Displaying weather data
- Isotherm — a line drawn on a map to join places of equal temperature.
- Isohyet — a line drawn on a map to join areas of equal rainfall.
- Isobar — a line drawn on a map to join areas of equal pressure.