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INTRODUCTION TO THE HYDROLOGIC CYCLE

A. INTRODUCTION    

Source: NASA Goddard Space Flight Center. Tropical Rainfall Measuring Mission. http://trmm.gsfc.nasa.gov/trmm_rain/Events/trmm_climatology_3B43.html

Source: NOAA Geophysical Fluid Dynamics Laboratory http://www.gfdl.noaa.gov/research/climate/highlights/GFDL_V1N5_gallery.html

Hydrologic Cycle Image credit: National Weather Service (2005) Jetstream: An Online School for Weather http://www.srh.weather.gov/srh/jetstream/atmos/hydro.htm

B. EVAPORATION: TRANSFER MOISTURE INTO THE ATMOSPHERE

Affected by:

• amount of available water

• sunlight

• temperature

• water vapor content of the air

• wind

Global Average Evaporation Rate 1988-2000 Based on NCEP-R2 Data Set

Image credit: NASA/GSFC (2007) Global Modeling and Assimilation Office http://gmao.gsfc.nasa.gov/research/merra/climate.php

C. HUMIDITY: MOISTURE IN THE ATMOSPHERE

Vapor pressure

• weight of the molecules of water vapor (mb)

• saturation vapor pressure

Mixing ratio

• grams of water vapor per kilogram of air (g/kg)

• saturation mixing ratio

Relative humidity

• ratio of the water vapor content of the air to the water vapor capacity of the air

• content: the actual amount of water vapor present

• capacity: the maximum amount of water that can be maintained in a gaseous state given the air temperature

Image credit: NASA/JPL (2006) New Global Maps Made from AIRS Data. http://airs.jpl.nasa.gov/News/Features/FeaturesNewGlobalMaps/

D. PRECIPITATION: TRANSFER MOISTURE OUT OF THE ATMOSPHERE

Image credit: ©Michael Collier. Image source: Earth Science World Image Bank http://www.earthscienceworld.org/images Stratocumulous clouds, Monument Valley, Arizona

Condensation

• clouds

• fog

Dew point temperature

Cooling mechanisms

• radiation cooling (contact cooling)

• uplift

Precipitation

• collision-coalescence process

• Bergeron ice crystal process

• Spatial precipitation patterns     

Image credit: National Weather Service Climate Prediction Center (2002) NOAA, Mean annual precipitation 1979-1995. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/wayne/annual.precip.html

Image credit: National Weather Service Climate Prediction Center (2002) NOAA, Mean annual precipitation 1979-1995. http://www.cpc.noaa.gov/products/precip/realtime/clim/annual/monthly/annual.html

E. SUMMARY

• Evaporation

• Humidity

• Condensation

• Precipitation

Image credit: Ralph F. Kresge, NOAA Photo Library, Historic NWS Collection http://www.photolib.noaa.gov/historic/nws/wea02054.htm