rainfall

• precipitation is the collective name for any water which falls to the ground- eg rain, snow, sleet or hailstones
• when air carrying evaporated water rises and cools, the water vapour cools to form water ( which falls as rain) or (if it’s very cold), rain, snow, sleet or hailstones
• rises, cools , condenses, cloud, precipitation
• snow forms when water vapour condenses very quickly and turns straight into ice crystals
• sleet is a mix of snow and rain
• hailstones begin as rain, but if a raindrop is carried upwards in a current of air, it will freeze to become a hailstone. each time this happens another layer of ice is added
• a rain gauge can be used to measure rainfall. these should:

  • be situated away from buildings ( which could shelter it)
  • should not be on tarmac ( tarmac is expensive to dig up, and rain bounces off it)
  • should be 30cm off the ground as only collects rainfall
  • should be sunk into the ground so it doesn’t fall over