MEPX
Chapter 3 of 10All chapters
  1. 1Weather against climate
  2. 2The engine
  3. 3Water in the air
  4. 4Forecasting
  5. 5The climate system
  6. 6The greenhouse effect
  7. 7A changing climate
  8. 8Consequences
  9. 9Responses
  10. 10Reading claims about climate

Chapter 3 of 10

Water in the air

Clouds, rain and humidity.

Condensation

Warm air holds more water vapour than cold air. Cool it enough and vapour condenses into droplets, forming cloud; grow the droplets enough and they fall.

  • Anything that lifts air makes it rain: mountains, fronts, heating from below.
  • Relative humidity compares the vapour present with the maximum at that temperature.

Storms

Thunderstorms need moisture, instability and a lift. Hurricanes need warm ocean, moisture and low wind shear, which is why they form in specific seasons and places.