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Journal Question :Journal Question What is pressure and what does it have to do with the weather?
Air Pressure & WindsLab Investigation Two :Air Pressure & WindsLab Investigation Two Tony Verde
Atmospheric Pressure :Atmospheric Pressure -a measure of force that gas molecules in the atmosphere exert onto the surface of the earth
Slide 4:Imagine a one-inch cube of air. Now imagine a stack of one-inch air cubes that reaches from the ground all the way to the edge of the Earth’s atmosphere. That stack of air cubes actually weighs 14.7 pounds. Measured in millibars (mb)Atmospheric Pressure is 14.7 pounds per square inch at sea level.
Pressure is an effect which occurs when a force is applied on a surface. :Pressure is an effect which occurs when a force is applied on a surface. The symbol of pressure is p (lower case).
Mathematically:
p = F/A
where:
p is the pressure,
F is the normal force,
A is the area.
Two types of air pressure: :Two types of air pressure: High pressure
associated with clear, cool weather. Around high-pressure systems, winds flow clockwise in the northern hemisphere
The air moving away from the High pressure system leaves a "hole" to be filled, so air from above sinks into that "hole".
tends to block or deflect approaching bad weather
Slide 8:Low pressure
winds around the system move counterclockwise
Pushes any air that was there up. As the air rises, water vapor condenses into clouds that can bring precipitation.
Associate low pressure with storms or deteriorating weather
Pressure on a map :Pressure on a map Meteorologists indicate areas of different pressure on a map using lines
Areas that have the same pressure are connected by a line called an isobar. isobar
"pressure gradient force“ - PGF :"pressure gradient force“ - PGF A net force that is directed from high to low pressure and this force is called the "pressure gradient force".
PGF triggers the initial movement of air
pressure gradient force :pressure gradient force pressure gradient force calculation
PGF = (High Pressure – Low Pressure)/ distance
I.e. low pressure = 1000 mb
High pressure = 1010 mb
Distance 80 km
(1010 – 1000)/80 = .12 PGF is equal to .12
Why do differences in pressure cause wind? :Why do differences in pressure cause wind? Wind is the result of high and low pressure differences attempting to equalize their pressure differences. air will flow from high pressure in toward the low pressure
Barometric Pressure :Barometric Pressure Changes in pressure are measured with a barometer