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Atlas 2m thermal infrared image, Atlanta, GA

Atlas 2m thermal infrared image, Atlanta, GA. Units: kW/m 2 /day Source: R. L. Sass, Rice Univ., Houston, TX http://www.ruf.rice.edu/~sass/UHI.html. Atmospheric Moisture. Environmental Significance of Water. Important component of global energy fluxes (latent heat)

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Atlas 2m thermal infrared image, Atlanta, GA

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  1. Atlas 2m thermal infrared image, Atlanta, GA

  2. Units: kW/m2/day Source: R. L. Sass, Rice Univ., Houston, TX http://www.ruf.rice.edu/~sass/UHI.html

  3. Atmospheric Moisture

  4. Environmental Significance of Water • Important component of global energy fluxes (latent heat) • Powerful agent of erosion • Universal solvent – transports nutrients and contaminants • Required for biological processes – availability determines species distributions

  5. Outline • Hydrologic cycle (water balance) • Atmospheric moisture (precipitation) • Clouds and implications for climate change

  6. 1. Hydrologic Cycle

  7. Hydrologic Cycle

  8. Water Balance Describes the relationship among fluxes of water Land surface Oceans Precipitation Input Input Evaporation Transpiration Output -- Output Runoff Output Input Land: Precipitation = Runoff + Evapotranspiration Oceans: Precipitation + Runoff = Evaporation

  9. Water Balance Describes the relationship among fluxes of water Land surface Precipitation Input Evaporation Transpiration Output Runoff Output Land: Precipitation - Evapotranspiration = Runoff

  10. 2. Atmospheric Moisture

  11. Atmospheric Moisture Amount of moisture held in air depends upon air temperature 26 g/kg 15 g/kg 2 g/kg

  12. Dew point temperature Atmospheric Moisture http://www.weather.com Dew point temperature: Temperature of an air mass at which it is saturated with moisture

  13. Atmospheric Moisture http://www.weather.com Relative humidity: Amount of water vapor currently in air relative to what air could hold at that temperature if saturated If air on 70o F day held 5 g/kg water, RH = 5/15 = 33%

  14. Atmospheric Moisture Who cares?

  15. Atmospheric Moisture As air rises, it cools. Cooler air holds less mositure Adiabatic Cooling

  16. Atmospheric Lifting Mechanisms Convection – local heating

  17. Atmospheric Lifting Mechanisms Orographic Lifting – topographic barriers

  18. Atmospheric Lifting Mechanisms Frontal Lifting – cold / warm air masses

  19. Atmospheric Lifting Mechanisms Convergence – high / low pressure gradients

  20. Monga Bay, Peru

  21. Worldwide annual precipitation

  22. 3. Clouds

  23. Clouds

  24. Clouds

  25. Clouds Cloud form • Stratiform - horizontal • Cumuliform - vertical • Cirroform – wispy, ice crystals

  26. Role of Clouds in Global Climate System http://www.giss.nasa.gov/research/briefs/delgenio_03/

  27. Role of Clouds in Global Climate System

  28. Role of Clouds in Global Climate System

  29. High clouds – Less reflective, absorb longwave radiation Role of Clouds in Global Climate System Low clouds – reflect shortwave radiation

  30. Global albedo with clouds Role of Clouds in Global Climate System Global albedo without clouds Source: E. F. Harrisson et al., http://eumetcal.meteo.fr/euromet/english/satmet/s8220/s8220210.htm

  31. Role of Clouds in Global Climate System

  32. Diurnal (day-night) variations in longwave radiation Role of Clouds in Global Climate System Global longwave radiation Source: Eugene S. Takle, 2006 http://www.meteor.iastate.edu/gccourse/influ/influ_lecture_new.html

  33. Implications of clouds for climate change • Surface warming may induce more cloud formation • Clouds reduce incoming shortwave (albedo) • Clouds increase counterradiated longwave (greenhouse gas) • Clouds introduce considerable uncertainty to climate change scenarios

  34. Summary • Hydrologic cycle describes processes controlling fluxes of water • Water balance used to describe relationship between precipitation, runoff and evaporation/transpiration • Moisture content of air is temperature dependent (warmer air holds more moisture) • Air must be cooled for precipitation to occur (atmospheric lifting mechanisms)

  35. Summary (cont.) • Atmospheric lifting creates clouds. • Clouds have varying effects on net radiation • Effects of climate change on cloud formation introduces considerable uncertainty into predictions

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