Transcript 4th gradeWeatherConditions

Weather
Conditions
What Makes up Earth’s
Atmosphere?
 The layer of air surrounds our
planet is called the atmosphere.
Layers of the Atmosphere




Troposphere
Stratosphere
Mesosphere
Thermosphere
Troposphere
 Layer closes to the
earth
 Weather happens in
this layer
 Live and breathe air in
this layer
 Air temperature
decreases as you go
higher
Stratosphere
 Airplanes travel in this
layer to avoid bad weather
 Contains most of the
atmosphere’s ozone
 Ozone protects living
things from harmful rays of
the sun
 Temperature increase with
height
Mesosphere
 Temperature decrease
with height
 Coldest layer of the
atmosphere
Thermosphere
 Hot, outermost layer
 Temperature increase
quickly with height
How Do Air Masses Affect the
Weather
Greenhouse Effect
Air Masses
What happens when to air masses
meet?
 When two air masses meet, they form a
border called a front
 A front is the area where two air masses
meet and weather happens
Cold Front
 A cold air mass
catches up with a
warm air mass
 The cold air mass
forces the warm air up
in the atmosphere
 As warm air
Cold Front
 As warm air pushes
upward, it cool and
forms cloud.
 Rain develops.
 Thunderstorm often
occur along a cold
front.
Cold Front
 Generally move from northwest
to southeast
 Air behind a cold front is colder
and drier than the air ahead of it.
 When a cold front passes
through, temperatures can drop
more than 15 degrees within the
first hour.
 Represented by a solid lines
with triangles along the front
pointing towards the warmer air
and in the direction of
movement
Warm Front
 Forms when a warm air
mass catches up with a
cold air mass
 Warm air slides up over
the colder, denser air
 Generally move from
southwest to northeast
 Air behind a warm
front is warmer and
more moist than the air
ahead of it
 Represented by a solid
line with semicircles
pointing towards the colder
air and in the direction of
the movement
 Steady rain or snow may
fall as the front
approaches and passes
Common Characteristics of Warm Fronts
While Passing
Before Passing
Winds
Temperatures
Pressure
Clouds
Precipitation
Visibility
Dew Point
South-southeast
After Passing
Clouds and Weather
 Weather scientists classify a cloud based on its shape, its
color, and where it forms in the atmosphere
Cirrus
 A wispy white cloud
 Fair weather
Cumulus
 Puffy cotton-ball
clouds
 Begins to form when
water droplets
condense at middle
altitudes
Cumulonimbus
 Dense cumulus cloud
with a hazy outline
 Usually producing
heavy rain,
thunderstorms, or
hailstorms
Stratus
 Dark gray clouds that
form a low layer
 Sometimes bring rain
or snow showers
What is a Cycle?
 A sequence of events
that repeat themselves
Evaporation
 The sun heats up water in
rivers, lakes, or ocean
 The water changes from a liquid
into a gas, vapor, or steam.
 The water vapor leaves the
rivers, oceans, or lakes and
goes into the atmosphere.
Condensation
 Water vapor in the air
gets cold and changes
back into liquid
 forming clouds
Transpiration
 Is the process by which plants
return water to the atmosphere.
 After absorbing water from the
ground, plant release water
through their leaves.
 This helps plants stay cool.
Precipitation
 Occurs when so much
water has condensed that
the air cannot hold it
anymore.
 Clouds get heavy and
water falls back to earth in
the form of rain, sleet, hail,
or snow
What instruments do meteorologist
use to forecast weather?
Anemometer
 Measures wind speed
 The cups catch the
wind, turning a dial
attached to the
instrument.
 The dial shows the
wind speed.
Barometer
 Measures air pressure
Psychrometer
 Measures relative
humidity, using the
cooling effect of
evaporation
Hygrometer
 Measures the amount
of humidity in the air.