The Water Cycle

• hydrosphere contains 1.4 sextillion litres of water
• 97% saline water + 3% freshwater = 100% hydrosphere
• 69% cryosphere + 30% lithosphere groundwater + 0.3 surface + 0.04% water vapour in atmosphere = 100% freshwater
• solid turns to gas by sublimation
• gas turns to solid by deposition
• water must be physically & economically accessible to use = only small amount available
• gain energy = melt/boil
• lose energy = condense/freeze
• Global Hydrological Cycle :


  water continuously cycled between different stores (closed)
• amount of water in stores varies over local to global scales
• evaporation :


  liquid turns to gas = water vapour
• evaporation :


  . when water gains energy from solar radiation

  . increases amount stored in atmosphere

  . magnitude of flow depends on season & location

  lots of solar radiation + large water supply + warm dry air = high evaporation
• condensation :


  water vapour to liquid
• Water cycle flows :

  1. Evaporation
  2. Condensation
  3. Cloud formation & precipitation
  4. Cryospheric processes
• condensation :

  . loses energy to surroundings

  . when air containing water vapour cools to dew point

  magnitude depends on:

  1. amount of vapour in atmosphere
  2. temperature (temp drop at night)
• precipitation : 


  . warm air cools = water vapour in it condenses into droplets = gather as clouds

  . droplets get big enough = fall as precipitation
• during periods of global cold inputs to cryosphere (snow) are higher than outputs (melting)
• Earth has extensive ice stores (Antartica & Greenland) and large volume of sea ice
• variations in cryosphere happen over long timescales
• annual temperature fluctuations are a short variation in cryosphere
• types of precipitation

  1. orographic
  2. frontal
  3. convective
• things that cause warm air to cool

  1. other air masses
  2. topography
  3. convection
• Frontal Precipitation

  • caused by other air masses
  • warm air is less dense than cool air so when they meet its forced above and cools as it rises = frontal precipitation
• Orographic Precipitation

  warm air meets mountains 🏔️ (topography) its forced to rise = cools = orographic precipitation
• convection causes convective precipitation
• Convective Precipitation

  sun heats up ground = moisture on ground evaporates = rises up as column of warm air = cools = convective precipitation
• Convection definition

  the movement of particles, transporting their heat energy from hotter areas to cooler areas
• examples of cryospheric processes

  1. accumulation
  2. ablation
• accumulation

  overall gain in mass of frozen water (ice or snow)
• ablation

  overall loss of mass of frozen water (ice or snow) due to melting