The Global Hydrological Cycle

• The amount of water available on the earth is finite 
  
• the total amount of water does not change because there is a closed system
• This means there are no inputs from outside, and nothing is lost
• Two processes, solar energy and gravitational potential energy drive the system

Warm Climate = More evaporation = increased moisture levels in the atmosphere

Increased comdensation as air cools = Greater precipitation

Keeps water moving through a series of inputs, outputs, stores and flows

outpusts govern inputs

• Solar energy concentrated in the extremes
• Evaporation from the sea produces high rainfall
• 74% world's rainfall occurs at sea
• Seasonal monsoons and droughts of Asia and Africa contrast with the temperate climates of North West Europe