Download Weather Crash Course Water Cycle

Weather Crash Course
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
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.
Warm Air vs. Cool Air
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.
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.
Sea Breeze
During a warm
day, the land
heats and the
cool air from
the ocean cool.
moves in to
the land.
Land Breeze
During the
night, the land
cools. The air
over the land is
It moves
over the out to
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.
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.
Weather Fronts
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.
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.
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