Weather Processes & Phenomena

• • Evaporation
  • Condensation
  • Sublimation - solid to gas
  • Deposition - gas to solid
• Humidity - Amount of water in the atmosphere

  Relative humidity - water vapour present as a % of max amount the air at that temp can hold
• Convectional Rainfall

  • Hot land heats air above it
  • Air rises - cooling and condensation occurs
  • Rain falls - common in tropical and summer areas
• Frontal Rainfall

  • Air forced to rise of barrier
  • Cools and condenses
  • Rain shadow effect
  • Rain falls
• Frontal Rainfall

  • Warm air meets cold air
  • Warm air rises as less dense
  • Cools & condenses
  • Common in mid latitudes where warm tropical and cold polar converge
• Radiation Cooling

  • Low-lying areas in calm weather
  • At night - cool air cools ground - cooled to dew point
  • condensation occurs
  • causes radiation fog
• Clouds

  • Water droplets held in suspension
  • Stratiform (layers) or Cumuliform (heaped)
  • Unstable conditions = cumulus clous due to convection uplift
• Rain

  • 0.5 - 5mm
  • drizzle <0.5mm
• Hail

  • Concentric rings of frozen water
  • Raindrops carried up & down in air currents in cumulonimbus clouds
  • Freezing & Partial melting
• Snow

  • Frozen precipitation
  • temp below freezing point & water vapour converted to solid
  • Air must be moist
  • Warm moist air hits cold front = snow
• Fog

  • Radiation - Earth’s surface cools air to dew point
  • Condensation occurs creating fog
  • Advection
  • Warm moist air flows horizontally over cooler land/sea