1. Surface Water Balance (1)

2. Review of last lecture: Surface energy balance dT/dt SWdn =Scos  SWup =SWdn  LWdn =  Tair 4 LWup =  Ts 4 LH=  C d LV(q surface - q air ) SH=  C d C p V(T surface - T air ) Fc = - dT/dz Incoming shortwave + Incoming longwave = Reflected shortwave + Emitted longwave + Latent heat flux + Sensible heat flux + Subsurface conduction  What is sensible heat flux? What is latent heat flux? Bowen ratio B= SH/LH = C p (T surface - T air ) / L(q surface - q air ) provides a simple way for estimating SH and LH when the net radiative flux Fr is available LH=Fr/(B+1), SH=Fr B/(B+1) Factors affecting soil thermal conductivity Other heat sources: precipitation, biochemical, anthropogenic

3. The global water cycle

4. Components of global water cycle Ocean water Land soil moisture, rivers, snow cover, ice sheet and glaciers Sea ice Atmosphere water vapor, clouds, precipitation Water in biosphere (including human beings)

5. Component I: Ocean Covers 70% of the Earth’s surface

6. Observed Changes in Global Sea Level

7. Observed Changes in Sea Level Largest in the western part of ocean basin

8. Observed Changes in Ocean Heat Content

9. Component II: Land Soil moisture

10. Component II: Land >1000 major rivers flow on the seven continents Amazon river (#1)Yangtze river (#4)Mississippi river (#6)

11. Component II: Land Snow cover

12. Observed Changes in Snow Cover: Significant melting

13. Component II: Land Ice sheet

14. Retreat of Greenland Ice Sheet – a huge contributor to sea level rise today Greenland is responsible for about 10% of the observed global sea level rise and accelerating. Greenland holds 7 m of sea level equivalent.

15. Component II: Land Glaciers

16. Retreat of Mountain Glaciers: a major contributor to sea level rise IPCC (2001) Glacier retreat is a world-wide phenomena. Will affect water supply for millions: Kenya/Tanzania Northern India Andes Mountains

17. Melting in Glacier National Park

18. Component III: Sea ice

19. Observed Changes in Arctic Sea Ice: Significant melting

20. Reduced Arctic sea ice: A result of warming that leads to more warming

21. Component IV: Atmosphere Water vapor flows in the atmosphere

22. Observed Changes in Water Vapor Significant increase

23. Component IV: Atmosphere Clouds drifts with the winds

24. Component IV: Atmosphere Precipitation drives many atmospheric circulations which in turn transport water around the world Hadley Circulation Monsoons Walker Circulation

25. Observed Changes in Precipitation: Significant change in many places

26. A significant fraction of the human body is water (~75%) The remaining: fat, protein, carbonhydrate, other solids

27. So the water in our bodies may come from … A stream in the Niagara Fall … A white cloud over the tropical Pacific … A raindrop in the Amazon rainforest … Therefore we need to protect the environment because any pollution we put into the environment may someday come back into our bodies An ice sheet in the Arctic Ocean…

28. Summary: Components of global water cycle Ocean water Land soil moisture, rivers, snow cover, ice sheet and glaciers Sea ice Atmosphere water vapor, clouds, precipitation Water in biosphere (including human beings)