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Cloud and Precipitation Notes
Water Cycle• Most of the Earth’s water is recycled• Oceans hold most of the water – Evaporation: The change of state from a liquid to a gas– Condensation: The change of state from a gas to a liquid– Precipitation: Water falls from clouds to the earth
How are clouds formed?• Made of condensed water vapor– Air cools as it rises and condenses into tiny droplets
or ice crystals– These tiny droplets/ice crystals are so light they
either float as clouds or fall very slowly
• Water must condense on something solid (Ex. dust, smoke, salt, etc.)
Characteristics of clouds
• Form under different conditions
• Shapes and sizes are determined by air movement
• Location is also a factor– Higher altitude = tiny crystals – Lower altitude = water
droplets/ice crystals
3 Main Types of Clouds
• Cirrus • Cumulus • Stratus
Two prefixes that help to describe clouds further are:
• Nimbo/nimbus – Produce
precipitation
• Alto–Medium
altitude
Cirrus Clouds• Means “curl of hair”• Form at high altitudes
in very cold air• It is made of ice• Wispy or feathery in
appearance• Normally found in fair
weather but can be a sign that a storm is approaching
Cumulus Clouds
• Means “heap” or “pile” • Puffy white clouds with darker bases• Usually appear in the daytime• Cooler air sinks along the sides of
these clouds keeping them apart• Cumulonimbus clouds are ones that
produce thunder storms, they are also called thunderheads
Stratus Clouds• Means “spread out”• These are the clouds that produce ‘grey’ skies• They form in flat layers when air cools over
large area without rising• They are smooth because they form without
strong air movement
Fog• A cloud that rests on the ground or a body of water• If forms when a surface is colder than the air above it• Heaviest at dawn• It can be a safety hazard while driving because it
makes it hard to see what is in front of you
What is precipitation?
• Any form of water that falls from the clouds and reaches Earth’s surface
• Cloud droplets are much smaller than a typical raindrop• Precipitation always comes from clouds but not all
clouds form precipitation– What types of clouds do?
Formation
• Cloud droplets (water) or ice crystals must grow heavy enough to fall through the air.
• They get heavier by colliding or combining with other droplets.
Measuring Precipitation
• Rain Gauge• Measuring snow
Types of Precipitation• Rain• Sleet• Freezing Rain• Snow• Hail
Rain
• Most common form
• .5mm in diameter
• Fall from nimbostratus clouds
Rain
Sleet
• When there are layers of warm air and cold air in the sky.
• As droplets fall they freeze into solid ice particles
Sleet
Freezing Rain
• Raindrops falling through cold air that don’t freeze until they reach a cold surface (the ground)
• Looks like sleet as it falls but freezes on the surface instead of right before it hits the surface
Freezing Rain
Freezing Rain vs. Sleet
• What is the difference between the two pictures?• Which is freezing rain and which is sleet? WHY?
Snow• Ice crystals grow and merge
to form snowflakes• Variety of shapes and sizes• Most have 6 sides or
branches• When they fall through moist
air that is near freezing they clump together
• When falling through colder drier air they don’t
Hail• Only forms inside
cumulonimbus clouds
• Strong updrafts carry the ice pellets up and down causing the pellet to get bigger
• When it gets to heavy it falls to the ground
Hail
Acid Rain• Forms when factories, power plants, automobiles
and some natural sources release sulfur dioxide and nitrogen oxides into the air
• They combine with the water to form sulfuric acid and nitric acid
• This acid rain can affect trees, lakes and damage the surface of buildings and sculptures
Acid Rain damage
How Acid Rain Forms