Moisture, Clouds, and Precipitation Pt. 2
Clouds are classifies on a basis of their
form and height
high, white, thin
cloud masses that consist of rounded individual masses
sheets or layers that cover most or all of the sky
cirrus, cirrostratus, cirrocumulus
flat layers of clouds
consist of fluffy masses
consist of rounded masses
Altocumulus clouds differ from cirrocumulus clouds in that
altocumulus clouds are larger and denser
create a uniform white to gray sheet that covers most to all of the sky with the sun or moon as a visible bright spot.
stratus, stratocumulus, nimbostratus
have a scalloped bottom that appears to be long parallel rolls or broken rounded patches.
Main precipitation makers
a cloud with its base at or very near the ground.
Fog caused by cooling
As the air cools, it becomes denser and drains into low areas such as river valleys, where thick fog accumulations may occur.
Fog caused by evaporation
When cool air moves over warm water, enough moisture may evaporate from the water surface to produce saturation.
For precipitation to form
cloud droplets must grow in volume by roughly one million times
The Bergeron Process
A scientific theory that relates the formation of precipitation to supercooled clouds, freezing nuclei, and the different saturation levels of ice and liquid water.
is the condition of water droplets that remain in the liquid state at temperatures well below 0oC.
is the condition of air that is more concentrated than is normally possible under given temperature and pressure conditions.
Collision- coalescence process
a theory of raindrop formation in warm clouds (above 0oC) in which large cloud droplets collide and join together with smaller droplets to form a raindrop.
The type of precipitation that reaches Earth's surface depends on
the temperature profile in the lower few kilometers of the atmosphere.
drops of water that fall from a cloud with diameters of at least 0.5 mm.
At very low temperatures (when the moisture content of air is low) light fluffy snow made up of individual six-sided ice crystals forms.
the fall of clear to translucent ice
Hail is produced in
Hailstones begin as
small ice pellets
by collecting supercooled water droplets as they fall through a cloud
Water's boiling and condensing point
Water's freezing and melting point
A psychrometer measures what in addition to relative humidity