Download What is Weather?

• Weather is the
conditions of Earth’s
atmosphere at a certain
time and place.
• For example, sunshine,
rain, hurricanes, and
storms are all examples
of weather.
• Weather is different at
different places around
the world.
© Erin Kathryn 2016
• The atmosphere is the layers
of air that surround Earth’s
surface.
• Earth’s atmosphere has 4
layers: troposphere,
stratosphere, mesosphere and
thermosphere.
• Weather occurs in the first
layer of the atmosphere, the
troposphere.
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• The water cycle is the movement of water
into the air as water vapor and back to
Earth’s surface as precipitation.
• The water on Earth is
constantly changing
from one form to
another in a continuous
cycle that occurs over
and over again.
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• Evaporation - Water evaporates
(changes from a liquid to a gas) into
water vapor due to heat from the Sun.
• Condensation – Water condenses
(changes from a gas into a liquid) into
water droplets. These water droplets
form clouds.
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Different types of clouds bring various types of weather.
Cloud
Description
stratus
Low-level cloud that forms in layers and usually
brings rain
cumulus
Fluffy clouds that are flat on the bottom and
usually mean fair weather
cirrus
Thin clouds that look like feathers and form
high in the sky; usually bring fair weather
cumulonimbus
Tall clouds that bring thunderstorms
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Picture
Different types of clouds bring various types of weather.
Cloud
Description
fog
Cloud that forms close to the ground
altocumulus
Small, white, puffy, middle level cloud
stratocumulus
Low puffy, gray clouds that can sometimes
produce rain
cirrocumulus
High clouds that look like tiny cotton balls
bunched together
altostratus
Dark gray covering cloud that usually brings
rain
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Picture
• Precipitation- When clouds become too
heavy, the water droplets fall to
Earth’s surface in the form of rain,
snow, sleet, or hail.
• Collection– Precipitation collects in
rivers, streams, oceans, and lakes
allowing it to be evaporated and begin
the water cycle again.
© Erin Kathryn 2016
rain
Falling drops of liquid water
snow
Falls when the temperature in the cloud is
below freezing (32°F)
sleet
Rain that freezes as it falls to Earth’s
surface
hail
Forms when drops of rain freeze in the
cloud and are carried higher into the cloud
freezing over and over before falling to
Earth’s surface
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• Runoff- Precipitation that flows
downhill on Earth’s surface to rivers,
streams, lakes, and oceans is called
runoff.
• Infiltration– Some precipitation soaks
into the ground. This is called
infiltration or groundwater.
© Erin Kathryn 2016
• Weather conditions include temperature,
humidity, wind, and air pressure.
• Temperature – how hot or cold the air is
• Humidity – the amount of water vapor in
the air
• Wind – the movement of air
• Air pressure – the weight of air as it
presses down on Earth.
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Weather conditions can be measured using various weather
instruments.
thermometer
rain gauge
Measures the temperature of the air
Collects and measures the amount
of precipitation that has fallen in
an area
© Erin Kathryn 2016
Weather conditions can be measured using various weather
instruments.
barometer
anemometer
Wind vane
Measures air pressure
Measures the speed of
the wind
Measures the direction
of the wind
© Erin Kathryn 2016
• An air mass is a large body of air that has
about the same temperature, air pressure, and
moisture.
• Air masses are either warm or cold and either
moist or dry.
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• Warm air masses usually form near warm
places.
• Cold air masses usually form near cold
places.
• Moist air masses usually form over oceans.
• Dry air masses usually form over land.
• Most changes in weather happen when one
air mass moves into a place and pushes out
another air mass.
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• The place where two air
masses meet is called a
front.
• Weather can change
suddenly when a front
moves across an area.
• Many storms and
precipitation take place
along fronts.
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• When a cold air mass meets
a warm air mass a cold front
forms.
• The cold air moves under the
warm air, pushing it up.
• The warm air rises, clouds
and precipitation occur.
• Cold fronts often bring
thunderstorms.
• Cold front symbol on a
weather map 
© Erin Kathryn 2016
• A warm front forms when
a warm air mass pushes
into a cold air mass.
• The warm air slowly
moves up and over the cold
air forming layers of gray
clouds and steady
precipitation.
• Warm front symbol on a
weather map 
© Erin Kathryn 2016
• Meteorology is the study of weather.
• This involves the measuring of conditions near
Earth’s surface and high in the atmosphere.
• Meteorologists identify air masses and fronts.
• They also predict where they will move.
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• These predictions help
meteorologists create a
weather map.
• Weather maps are used to
help forecast the weather.
• Weather maps use symbols
to show the location of
fronts and precipitation.
• A forecast is a prediction of
what the weather will be for
a certain day, week, or longer
period of time.
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• Severe weather includes
hurricanes, tornadoes, and
snowstorms.
• Meteorologists study and
forecast storms using various
tools.
• Forecasters can give weather
warnings when severe
weather is likely to move
into an area.
• Warning give people time to
prepare or leave an area.
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• Climate is the usual weather conditions of a
place over an extended amount of time.
• Climate has a lot to do with the kinds of
plants and animals that can live and survive
there.
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• How much sunlight an area gets, oceans or
large bodies of water, altitude, and mountains
are all factors that affect climate.
• Scientists learn about climate by looking at
tree rings in old fossils and evaluating core
samples of ice to see how the layers of fossil
and ice have changed over time.
© Erin Kathryn 2016