weather

• Weather: Short-term day to day changes in the atmosphere in a place.
• Climate: The average weather conditions in a particular area over a long period of time.
• Stevenson Screen:

  • Double roof to protect from sun's heat.
  • Painted white to reflect sun's heat.
  • Raised 110 cm above ground to avoid effects of ground surface.
  • Slated sides to allow entry of air.
  • Wood not metal, as metal conducts heat.
  • Sited in open space to avoid external influences e.g. heat from buildings.
• Inside a Stevenson Screen:

  • Sometimes a barometer - air pressure.
  • Wet-and-dry bulb thermometer - indicates the humidity of the air.
  • Maximum - minimum thermometer - records the max and min temp.
• Advantages of using digital instruments:

  • Greater accuracy.
  • Human errors are removed.
  • More exact readings.
  • Automatic recording.
  • Instant analysis.
• Record cloud types:

  • Choose same times during the day over a period of one week.
  • Observe of several times each day.
  • Identify cloud types using shape of clouds.
  • Estimate cover.
  • Record names of cloud types in a table/chart.
  • Record clouds in eights.
• Wet-and-dry bulb thermometer:

  • Measures humidity
  • Read off wet and dry bulb temps.
  • Use relative humidity table/chart.
  • Work out difference between the two.
  • Read off figure at intersection of dry bulb and wet bulb depression figures.
• Barometer: Measures air pressure in millibars.
• Max/min thermometer: displays the maximum and minimum temperatures of the day
• Wet/dry bulb thermometer: measures humidity.
• Rain gauge: Measures rainfall. Should only be placed on grass.
• Main features; rain gauge:

  • On grass, to avoid splashes entering the gauge.
  • Part buried to prevent evaporation and stability.
  • No trees overhanging to prevent drips entering the gauge.
  • Away from buildings to avoid too little rain entering.
  • Stand vertically upright to keep the correct diameter.
  • The height of the water in the small cylinder measured.
• Cloud cover:

  • The amount of sunshine reaching the ground depends on the amount and duration of any cloud cover.
  • Given in units called oktas.
  • Each okta represents one eigth of the sky covered by cloud.
• Heliograph:

  • Records the amount of sunshine at a given location.
  • Burns a timeline.
  • Traces sunshine not hours of daylight.
  • The ball focuses the light and burns a line onto the cord.
• Wind vane: checks direction of wind.
• Anemometer: measures wind speed in mph/kph or m/s.
• Why should an anemometer be on the roof?

  • If higher up, no interference from trees and buildings.
  • It will not be sheltered, ground may be sheltered by buildings.
  • On the roof it cannot be damaged by people.
  • Results will be accurate.
  • No wind chanelling.
• Westerly wind: blows from west to east.
• Cirrus clouds:

  • Found in high atmosphere - usually over 5,500 metres.
  • Common throughout the world.
  • Thin and wispy in appearance.
  • Move fairly quickly.
• Stratus clouds:

  • Low level - below 2,000m and sometimes reaching ground.
  • Usually grey and move fast.
  • Can produce light rain and snow.
• Cumulonimbus clouds:

  • Large clouds up to 10 km high and across.
  • They resemble a giant cauliflower.
  • Produce rain, thunder and lightening.
  • Usually found in spring and summer.
• Cumulus clouds:

  • Fairly low clouds with bottom between 600 m and 1,200 m.
  • Looks like lumps of cotton wool.
  • Can produce light rain.
  • Individual clouds have a short life cycle.
• Relief rain: Rain that falls on the ground and is absorbed by the soil.
• Frontal rain: Rain that falls in a straight line from the front of a storm.
• Convectional rain: Rain that is formed when warm air rises and cools, causing water vapour to condense.