Terms related to the processes for transforming energy into water



Terms related to the processes for transforming energy into water
Lecture 3
Introduction to Global Hydrological Cycle
• Basic Processes
• Global Water Reservoirs
• Global Water Transport
• Terms to Remember
Evaportion is a process of
transforming liquid water at the
surface to gaseous water in the
Condensation is a process of
gaseous water molecules condensing
on nuclei to become liquid or solid
• Liquid precipitation: rainfall, drizzle, dew,
• Solid precipitation: snow, hail
Ground Water
Subsurface water in soils and rocks
that are fully saturated
Transpiration is the process of water
loss through the stomates of plant
leaves during photosynthesis.
Evapotranspiration = Evaporation + Transpiration
Streamflow resulting from gravity on
water in channels of varying size from
the smallest trickles to the largest
Global Water Cycle
represents the largest
movement of matter
at the Earth’s surface;
associates with the
global climate system;
affects human
activities (population
distribution, industry,
transportation, etc.)
Ward and Robinson (2000)
Global Water Distribution and Characteristics
1. Ocean
Largest store
Little limitation to evap.
Heat redistribution
Low turnover rate
2. Terrestrial Waters
(1) Deep Groundwater
Low turnover
Amount uncertain
Poor quality
3. Atmospheric Waters
Smallest store
directly related to climate
affects vegetation
high turnover
(2) Shallow Groundwater
14 times higher turnover
14% of freshwater
Important source for humans
(3) Soil Water
Often unsaturated
Important to Agri./ecosystems
Affects ET, T. and heat flux
(4) Lakes/Inland Waters
Useful if fresh
High turnover
Accumulate pollutants
(5) Rivers
Smallest store over land
High turnover
Most important to humans
Balances the land-ocean system
(6) Terrestrial Ice
Consists of snow cover and glaciers
85% of fresh water
Small runoff
Sensitive to climate change
Very low turnover
Exchange between reservoirs
Global water vapor distribution
September 6, 2005, 00:15 UTC
Nine Year Global Monthly Mean
Soil Moisture Variation (1992-2000)
Vienna University of Technology
Terms to Remember (2)
2 Fluxes: Average
or instantaneous rate of water flow (gaseous, liquid,
solid) per unit surface per unit time, i.e. g/(m2 s), or g/(m2 d), or mm/d,
mm/h. All hydrological processes involve the flow of water, i.e. water
fluxes. Hydrological cycles results from fluxes between reservoirs.
3Recycling time: Time that a hypothetical water molecule to return to the
same point in a cycle. Usually involves more than one processes
4Turnover rate (residence time): Time required to empty (completely)
and recharge a storage
EEnergy: Hydrological cycles require energy and are driven by the solar
energy, either directly or indirectly at the global scale.
Terms to Remember (2)
Terms related to the processes for transforming energy into water
• Latent heat of vaporization: energy required for transforming water
in liquid forms to gaseous forms
• Latent heat of melting: energy required for transforming water in
solid forms to liquid forms
• Latent heat of sublimation: energy required for transforming water in
solid forms directly to gaseous forms
Heat related terms:
• Specific heat of water (Cw): heat energy per unit volume of water,
i.e., J/m3
• Specific heat capacity of water: the amount of energy required to
increase water temperature by one temperature unit, i.e., J/(m3 K)

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