1. Lecture 3 Introduction to Global Hydrological Cycle Basic Processes Global Water Reservoirs Global Water Transport Terms to Remember

2. Evaporation Evaportion is a process of transforming liquid water at the surface to gaseous water in the atmosphere.

3. Condensation Condensation is a process of gaseous water molecules condensing on nuclei to become liquid or solid water

4. Precipitation Liquid precipitation: rainfall, drizzle, dew, mist Solid precipitation: snow, hail

5. Ground Water Subsurface water in soils and rocks that are fully saturated

6. Transpiration Transpiration is the process of water loss through the stomates of plant leaves during photosynthesis. Evapotranspiration Evapotranspiration = Evaporation + Transpiration

7. Runoff Streamflow resulting from gravity on water in channels of varying size from the smallest trickles to the largest rivers.

8. 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.)

9. Global Water Distribution and Characteristics

10. Reservoirs 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 (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 3. Atmospheric Waters Smallest store directly related to climate affects vegetation high 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

11. Exchange between reservoirs

12. Global water vapor distribution September 6, 2005, 00:15 UTC http://www.ghcc.msfc.nasa.gov/GOES/globalwv.html

13. Nine Year Global Monthly Mean Soil Moisture Variation (1992-2000) http://www.ipf.tuwien.ac.at/radar/ers-scat/animation_frame.htm Vienna University of Technology

14. 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/(m 2 s), or g/(m 2 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.

15. 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 (C w ): heat energy per unit volume of water, i.e., J/m 3 Specific heat capacity of water: the amount of energy required to increase water temperature by one temperature unit, i.e., J/(m 3 K)