Name: _____________________________________________ Date: _______________ Period: ___________
18.3 Cloud Types & Precipitation
I. Classifying Clouds
•
Clouds are ____________________________, either droplets of water or tiny ice crystals.
•
Clouds are classified on the basis of their ______________ and __________________.
•
Three basic forms:
– _________________
• “Cirrus” means __________________________.
• Occur in _______________________________________.
• Have a ___________________________________ appearance.
– _______________________
• “Cumulus” means __________________.
• ____________________________________________ clouds with a flat base and rising
dome or tower.
• _________________________________ structure.
– ____________________
• “Stratum” means _______________________.
• Sheets or layers that cover the sky.
• No ________________________ clouds.
•
Three basic height classes:
– High: bases above ____________________
– Middle: occupy _______________________________
– Low: below ______________________
II. Specific Cloud Types
•
________________ clouds
– Three cloud types found:
• Cirrus: ____________________________________
• Cirrostratus: ____________________________________________
• Cirrocumulus: _________________________________
– All are thin, white, & made up of ________________________________ because of low
temperatures and little water.
•
________________ clouds:
– Prefix ________________ as part of the name
– Two types found:
• Altocumulus: fluffy masses that are _____________________________________________
________________________________________
• Altostratus: uniform _____________________________________ sheet that is thick enough
to make the moon or sun only a _________________________________
•
Can bring infrequent snow or light drizzle
•
_____________ clouds:
– Three types found:
• Stratus: _________________________________________________________ that covers
much of the sky
– May produce ____________________________________
• Stratocumulus: stratus clouds that have a _______________________ bottom that looks like
____________________________ or _________________________________________
• Nimbostratus: ___________________________________ that covers the entire sky
– “Nimbus” means __________________________ these clouds are one of the main
precipitation makers
•
Clouds of Vertical Development
– Certain clouds do not fit into a height category because their bases are at __________ height, but
they extend into the _____________________________________ level altitudes
– Associated with ______________________ air
– Two main examples:
• Cumulus: “__________________________” clouds that can grow dramatically under the
right conditions
• Cumulonimbus: a ___________________ cloud that grows dramatically to bring _________
__________________________________________________________________
– The flat top of it is called the “__________________________________”
III. Fog
•
There is no ______________________ difference between clouds & fog; they differ in _______________
_________________________ they form.
•
Fog is defined as a cloud with its base ______________________________________________________.
•
Two ways fog forms:
– Fog caused by ____________________:
• Warm air moves over cooler ground, cools, and condenses
• Often happens on cool, clear nights when the Earth’s surface cools rapidly by
_________________________
– Fog caused by ________________________:
• “______________________” appearance
• Often occurs over bodies of ______________that are _______________ than the air above
IV. How Precipitation Forms
•
Most cloud droplets are less than _________________________________ in diameter (0.020 mm).
•
For precipitation to form, cloud droplets must grow in ________________ roughly
_________________________ times.
•
Precipitation forms differently depending on the ______________________________ of the cloud.
– _____________cloud precipitation forms through the ____________________________________.
• Water droplets become ___________________________ (below 0°C)
– Pure water suspended in air doesn’t freeze until ________________.
– Supercooled water freezes readily when it hits a solid object
(______________________________________).
• When the air is ______________________________ with respect to ice (greater than 100%
humidity), ice crystals and water droplets cannot coexist.
– Rapid growth of ____________________________ results.
– Large ice crystals hit supercooled water droplets, forming even larger ice crystals that
are heavy enough to fall.
» Results in ____________________ when the surface temperature is less than
___________________ or in hotter weather, _______________.
– _______________ cloud precipitation forms raindrops through the _________________________
__________________________________________________.
• _________________________________________________ (like salt) form larger droplets.
• These droplets collide and coalesce (__________________________) with smaller droplets.
• When the droplets become heavy enough, they fall as ______________.
V. Forms of Precipitation
•
The type of precipitation that hits the ground depends on the ____________________________________
____________________________________________________ of the atmosphere.
– Rain & snow: drops of water with at least a diameter of ________________.
• Temp. above 4°C: ______________
•
–
–
–
Temp. between −5°C & 4°C: ___________________________________________________
_________________________________________________________________
• Temp. below −5°C: light, fluffy snow
Sleet: small particles of ___________ that form when a layer of air __________________________
____________________ overlies a layer of __________________________air near the ground
Glaze: also known as ____________________________________, occurs when rain becomes
____________________________ and freezes upon ____________________
Hail: produced in __________________________________ clouds, small ice pellets grow by
collecting ___________________________________________ as they fall, then hit an
______________________ and continue growing as they fall again; may happen many times before
it falls to the ground