THE HYDROLOGIC CYCLE

A true cycle with no beginning or end.

Nice and Simple...

The Hydrologic Cycle  Defined as the movement of water on, above, and below the surface of the Earth.  Describes condensation of water vapor and formation of cloud droplets and eventually precipitation.

Three Main Elements of H2O Cycle  Evaporation  Condensation  Precipitation

EVAPORATION (Transpiration)  The process of transforming liquid water from the oceans and the soil to water vapor.  Water vapor is an invisible odorless gas that enters the atmosphere.

CONDENSATION  The process of changing water vapor back to liquid water.  The process of forming cloud droplets.  As water vapor rises, temperature decreases in the atmosphere and condensation begins in the formation of tiny cloud droplets.

PRECIPITATION  Cloud droplets collide and coalesce with neighboring cloud droplets.  As they grow in size and weight, cloud droplets form precipitation which falls from the sky as  liquid water particles (rain)  solid water particles (snow and hail)

Other Processes...  Freezing  Melting  Sublimation Sublimation is the phase change from solid to gas minus the intermediate step of forming liquid.  For example: The change from snow or ice to gaseous water without the step of liquid water formation.

Cloud Formation  Clouds are visible masses of condensed droplets or frozen crystals suspended in the atmosphere.  Clouds are divided into two main categories  Convective or Cumulus (in latin: piled up)  Layered or Stratus (in latin: layer)

Location of Clouds in Atmosphere  Cumulus and stratus clouds are divided into four more groups that distinguish the altitude location of the cloud.  LOW (up to 6,500 ft.) Stratus, nimbostratus, cumulus and stratocumulus  Characteristics of cumulus clouds  Dense  White and puffy (like cotton balls)  Associated with good weather

Locations continued...  LOW clouds (up to 6,500 ft.)  Characteristics of stratus clouds  Dark gray  Low lying  Uniformly stratified or layered covering the whole sky  Usually associated with rain  MIDDLE clouds (6,500-16,500 ft.)  Begin with prefix “alto”  Includes alto stratus and altocumulus

High Clouds  Above 16,500 ft.  In the cold region of the troposphere  Begin with prefix “cirro” or cirrus  Often whispy or transparent  At this altitude, water freezes so the clouds are almost always composed of ice crystals.  High clouds include cirrus, cirrostratus, and cirrocumulus.  Aircraft contrails form in this altitude range.

Questions?  Activity: “It’s Time to Get Cirrus With Clouds”