Name: _________________________________________________________ Date: 11/9/15 Period: _______ NOTES
Weather 2.3 and 2.4 Notes: Clouds and Precipitation
What is the Water
 Evaporation: the process by which a liquid changes into a gas
Cycle?
 Condensation: The process by which a gas changes into a liquid
 Precipitation: Any type of liquid or solid water that falls from the sky
 Steps:
1. Water evaporates from bodies of water, ground, etc.
2. Water vapor condenses to form clouds.
3. Water falls to Earth’s surface as precipitation.
How does water vapor
 Humidity: The amount of water vapor in the air
interact with air?
 Saturated: When the air is holding all the water vapor it can hold
 Relative Humidity: The amount of water vapor the air is holding compared
to the amount it could hold at that temperature
 Dew Point: The temperature at which the air is saturated with water vapor.
How do we measure
 An instrument that is used to measure relative humidity.
humidity?
 Also called a wet-and-dry bulb thermometer
How do clouds form?
 Clouds are made of condensed water vapor.
 As warm air rises in the atmosphere, it cools.
 When air cools to its dew point, water vapor condenses into tiny droplets,
or ice crystals.
 Water must condense on something solid. Air is filled with tiny particles
such as dust, smoke, and salt from the ocean. Water vapor condenses on
these particles.
Characteristics of
 Clouds have different characteristics because they form under different
clouds.
conditions.
 The shapes and sizes of clouds are mainly determined by air movement.
 Location affects the composition of clouds. Clouds that form at high
altitudes are made of tiny ice crystals. Closer to Earth’s surface, clouds
are made of tiny water droplets or a mixture of ice crystals and water
droplets.
Cirrus Clouds
 Cirrus clouds form in very cold air at high altitudes.
 Made of ice crystals.
 They have a wispy or feathery appearance.
 You will usually see cirrus clouds in fair weather.
 However they can be a sign of a storm approaching.
Cumulus Clouds
 Cumulus clouds are puffy white clouds with darker bases.
 There are several varieties of cumulus clouds.
 Usually they appear in the daytime in fair weather.
 If cumulus clouds keep growing taller, they can produce showers.
 The tallest clouds are cumulonimbus clouds or thunderheads.
Stratus Clouds
 Stratus clouds form in layers when air cools over a large area without
rising or the air is gently lifted.
 Stratus clouds are smooth because they form without strong air
movement.
 These clouds produce steady, light precipitation.
What is fog?
 Fog is a cloud that rests on the ground or water
What is precipitation?
 All precipitation comes from clouds.
 Scientists use a rain gauge to measure rain fall.
 Some precipitation freezes or melts as it falls through the atmosphere.
Rain/Drizzle:
 Most common form of precipitation.
 Formed from water droplets or ice crystals that melt as they fall.
 Usually comes from stratus clouds
Freezing Rain:
 Rain that freezes when it hits the ground or other surfaces.
 Covers surfaces with a coating of ice
Sleet:
 Rain that freezes into ice pellets while falling through cold air
Snow:
 Forms from ice crystals that merge in clouds.
 Temperature below freezing from cloud to ground
Hail:
 Forms when ice pellets move up and down in clouds, growing larger as they
gain layers of ice.