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 vapor 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”