Download Winds and Pressure Systems - CRHS

What is pressure?
Pressure is accumulative force of gas
particles
http://www.falstad.com/gas/
High Energy gas (HOT) has lots of
movement, therefore high pressure
Low Energy (COLD) has less pressure
How do we measure pressure?
Using a Barometer
The height of the
Mercury Column is
equal to the
pressure acting on
the surface of the
mercury
P = gh
P = (density)(gravity)(height)
Two Types of Pressure Systems Occur in
Nature
Low Pressure Systems - “Cyclones”
High Pressure Systems - “Anti-Cyclones”
Each type has specific characteristics related
to the behavior of the gases that make up the
system and how they interact with each other
High Pressure Systems “Anti-Cyclones”
Winds blow outward
and clockwise at
surface
Associated with
converging winds
higher in the
atmosphere
Weather: clear and
“fair”
Low Pressure Systems
Winds blow inward and
counterclockwise at
surface
Associated with
diverging winds higher
in the atmosphere
Weather: cloudy with
precipitation (rising air)
What is Wind?
Wind is the movement of Air
Wind forms as a result of three factors:
Pressure Gradient Force
Coriolis Effect
Friction with the Earth’s Surface:
Pressure Gradients
Air wants to move from high to low pressure
(greater pressure difference = higher speed)
Isobars = lines of equal pressure
Coriolis Effect: Same effect as for ocean
currents
Moving air (wind) is deflected to the right of
intended path
Creates rotational movement
Friction with the Earth’s Surface
As air moves across the Earth’s surface, it is
slowed by contact with features of the Earth’s
surface
This slows down surface level winds, but
also creates mixing because higher level
winds continue at higher velocities
Wind is measured using two devices
SPEED is measured using an
ANEMOMETER
DIRECTION is measured using a WEATHER
VANE
• Local Winds are caused by temperature
differences.
• Two common types include :Sea and Land
Breezes: Occur in coastal areas
• Sea Breeze
• During the day, the land warms up
because of the sun. Air rises over the
land.
• To replace this air, cooler air from the
sea flows towards the land (sea
breeze)
Sea and Land Breezes (cont’d)
• Land Breeze
• During the night, the ocean is warmer than
the land. Air rises over the ocean.
• To replace this air, cooler air from the land
flows towards the sea (land breeze)
Day = Sea Breeze
Night = Land Breeze
• Mountain and Valley Breezes
• Valley Breeze: During the DAY air on the
slopes of mountains heats up and moves
up the mountain slope
• Mountain Breeze: At NIGHT air near the
mountain top cools more quickly than air
lower down, so it flows down slope
towards the valley
Valley Breezes
Mountain Breezes