CLOUDS AND PRECIPITATION
CLOUDS
489
Cloud
a visible collection of water and other particles that are suspended in the air
The water may be in the form of tiny water droplets or ice crystals.
Classification
Clouds are named based on their appearance and the height of their bases (bottoms).
cirrus
stratus
cumulus
numbus
489-492
CLOUD SHAPES
whispy clouds
layers, flat sheets
puffy, cottonball shaped
dark rain clouds
CLOUD BASE HEIGHTS
high-level = cirrus
higher than 6 km
ice
thin, whispy cirrus, cirrostratus
mid-level = alto
2 – 6 km
water/ice
altocumulus, altostratus
low level = stratus
0 – 2 km
water
fog, stratus, nimbostratus, cumulostratus
all level = cumulus
low base, high top
water/ice
cumulonimbus, fair weather cumulus
STORM CLOUDS
nimbostratus
dark, flat clouds
near warm fronts
long periods of steady precipitation
cumulonimbus
dark, puffy clouds
thunderheads
near cold fronts
short periods of intense precipitation
Resources
U Illinois web page
Clouds pdf
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/home.rxml
http://nenes.eas.gatech.edu/Cloud/Clouds.pdf
PRECIPITATION
Precipitation
493
any form of condensed water or ice crystals that falls to the earth
snow
falling ice crystals that stay frozen
sleet / ice pellets
falling water droplets that freeze in the air and bounce when they hit the ground
snow falls through warm air (melts) then cold air (refreezes) before landing
freezing rain
falling water droplets change to ice upon impact with cold ground (below 0°C)
snow falls through warm air (melts) then freezes immediately when they hit the ground
rain
falling water droplets that stay liquid (ground is above 0°C)
hail
large balls of ice produced by updrafts in cumulonimbus clouds (July, August)
see Figure 15.8 p. 494