Transcript Weather Crash Course

Weather Crash Course
5th Grade Science Lab
Water on the Earth
• Water Cycle – the cycle of fresh water
between Earth’s surface and the
atmosphere, changing from liquid to gas
to liquid
• Evaporation: liquid to gas
• Condensation: gas to liquid
• Humidity – the amount of
water vapor in the air
The Air Around Us
• Air Pressure – the weight of the
air in a given area
• The higher in the atmosphere, the
less pressure there is. There is less
air to press down. Gravity pulls
everything down…including air. So, the
closer to the ground – the more air
pressure there is.
• Think about playing JENGA. It is easier to move the
blocks at the top of the tower because there is less
weight on them.
Are you hot or cold?
• Warm air is less dense, or
lighter, so it rises.
• Cool air is denser, or
heavier, so it sinks.
• As warm air rises in the
atmosphere it cools. As
cool air sinks toward the
ground it warms. This is a
cycle.
• As air descends toward
the ground, where
pressure is high, it
warms. The warming
process inhibits cloud
formation.
• As air rises into the
atmosphere, where
pressure is low, it cools.
The cooling aids in
condensation and the
formation of clouds.
What’s Blowing?
• Wind – air moving horizontally
• Air will naturally move where
there is less pressure. When the
air moves there is wind.
• When you squeeze a
balloon you apply
pressure to one end.
The air inside the
balloon moves to the
end of the balloon
where there is less
pressure applied.
Feel The Breeze
• Sea Breeze
– During a warm day the
land heats.
– The cool air from the
ocean moves in to the
land.
• Land Breeze
– During the night the
land cools.
– The air over the land
is cool.
– It moves out over the
ocean.
Water sources hold their temperature better than land. So,
the temperature of land changes a lot from day to night,
whereas the temperature of the water stays more stable.
The Winds Around the Globe
• Global Winds – Earth’s rotation causes the
wind to curve as it blows across its surface.
• This curve is called the Coriolis Effect.
• Prevailing Westerlies: blow from the west
• Polar Easterlies: blow from the east
• In the United States our winds blow west to
east.
Air Masses
• Polar – cold
• Tropical – warm
• Continental – land / dry
• Maritime – water / moist
• When two air masses meet they do not mix.
• A boundary forms between them called a
front.
• Fronts often cause rainy, unsettled weather.
The Line that Divides
• When a cold front
meets a warm front the
cold air moves under the
warm air. This causes
wind and thunderstorms.
After the storm the
temperatures are usually
cooler because the cold
front brought in cold air.
• When a warm front
meets a cold front the
warm air moves up and
over the cold air. There is
often precipitation that
will last for days.
Afterward the weather is
warmer because the
warm front brings in
warm air.
Causing A Spark
Thunderstorms and Lightning
• When intense heating causes air
to rise quickly there is an updraft
of wind. The rising moist air causes clouds
to form. Water droplets are forming rapidly
inside the cloud. When they begin to fall as
rain drops it causes downdrafts. The
passing updrafts and downdrafts rub
against each other causing static electricity.
When enough static builds up there is a
spark – lightning. The heat of the lightning
creates the sound of thunder.
What’s the weather like for you?
• Climate – average weather pattern in a region,
typically described using temperature and
precipitation
Temperature and
precipitation are
affected by…
1. latitude: distance
from the equator
2. bodies of water:
distance from a
body of water
3. wind patterns:
easterlies or
westerlies
4. altitude: how high
above sea level a
place is