Transcript Low Pressure Areas

The Atmosphere &
Hydrosphere
Storms
and Winds
Atmospheric Pressure
• The air around you is always
pushing on you-> Air Pressure
•
elevation = atmospheric
pressure
• Example: Ears “popping” at
change in elevation
Atmospheric pressure - example
• Air Pressure difference cause winds which
Low Pressure Areas
The Differences in the Atmospheric Pressures around
the world cause High and Low Pressure Zones- which
affect our WEATHER!
• Warm air expands & rises
• Causes-> condensation
to increase in
atmosphere, storms
• CYCLONE => a center of
low-pressure
• Example: unstable
weather
High Pressure Areas
The Differences in the Atmospheric Pressures around
the world cause High and Low Pressure Zones- which
affect our WEATHER!
• Cold air is dense and
sinks
• Causes => Stable, clear,
DRY weather
• Example: HOT summers
or bitter cold winters
• Can also cause
permanent EXTREME
DRY!
Global Winds
• Winds move heat and
cold across the Earth’s
surface
• Wind always flows from
high to low pressure
areas
Types of Winds
• Prevailing Winds
=> blow from the
same direction
most of the time
• Ex. Trade winds
== sail ships
across the ocean
This is how Columbus ended
up in the Bahamas instead of
the Northeast coast.
Types of Winds
• Doldrums => little
or no wind blows
Ex. area around the
equator
- Ships get caught
here
- Pirates hide in these
areas
Types of Wind
Westerlies
• Wind in the
Middle
Latitudes
• 23 ½ to 66 ½
• Also known as
the Jet
Stream
Pressure Zones Collide = Storms
• Fronts => when two air
masses of widely different
temperatures or moisture
levels meet
• Dry lines in Texas
= severe
thunderstorms
Storms
1. Middle-latitude
=> cold dry polar
air mixes with
moist warm
tropical air,
pushed by the jet
stream
ex. Thunderstorms,
tornados
2. Tropical => are usually
smaller & lack fronts but
can be strong
- Often occur in the
summer when the ocean
waters are WARM
- Ex. Hurricanes
(Atlantic)
Typhoons (Pacific)
Hurricane
Jeanne /Francis– (2004)
Hurricane Ike(2008)
Monsoon winds
Winds – depending on the location of place
winds may bring moist air and rain
(Monsoons-) or may leave an area dry.
Monsoons
Orographic Effect
• The ocean side of a
mountain (windward)
often has heavy rainfall.
The air loses moisture
as it goes over the
mountain and is drier
when it reaches the
other side (leeward),
this creates a rain
shadow.
Orographic Effect
Windward side
Leeward side
Nevada
California
Orographic effect
Orographic Effect
Storms
• Make a T-chart in your notes on pg.
17 and label as shown below
Bill Nye- Storms video
Things I know
New things I learn
now about Storms about Storms
Video link