lecture 3 introduction to global hydrological cycle basic processes global water reservoirs global...
TRANSCRIPT
Lecture 3
Introduction to Global Hydrological Cycle
• Basic Processes
• Global Water Reservoirs
• Global Water Transport
• Terms to Remember
Evaporation
Evaportion is a process of transforming liquid water at the surface to gaseous water in the atmosphere.
Condensation
Condensation is a process of gaseous water molecules condensing on nuclei to become liquid or solid water
Precipitation
• Liquid precipitation: rainfall, drizzle, dew, mist
• Solid precipitation: snow, hail
Ground Water
Subsurface water in soils and rocks that are fully saturated
Transpiration
Transpiration is the process of water loss through the stomates of plant leaves during photosynthesis.
EvapotranspirationEvapotranspiration = Evaporation + Transpiration
Runoff
Streamflow resulting from gravity on water in channels of varying size from the smallest trickles to the largest rivers.
Global Water Cycle
Ward and Robinson (2000)
Significance: 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.)
Global Water Distribution and Characteristics
Reservoirs1. Ocean
Largest store Little limitation to evap.
Heat redistributionLow turnover rate
2. Terrestrial Waters(1) Deep Groundwater
Low turnover Amount uncertain
Poor quality
(2) Shallow Groundwater 14 times higher turnover
14% of freshwaterImportant source for humans
(3) Soil Water Often unsaturated
Important to Agri./ecosystemsAffects ET, T. and heat flux
(4) Lakes/Inland Waters Useful if fresh
High turnoverAccumulate pollutants
3. Atmospheric WatersSmallest storedirectly related to climateaffects vegetationhigh turnover
(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 distributionSeptember 6, 2005, 00:15 UTC
http://www.ghcc.msfc.nasa.gov/GOES/globalwv.html
Nine Year Global Monthly Mean Soil Moisture Variation (1992-2000)
http://www.ipf.tuwien.ac.at/radar/ers-scat/animation_frame.htmVienna 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 fluxes
• 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)