Defined as the force exerted on you by the weight of tiny air particles in the atmosphere per unit area Earths atmospheric pressure 147 pounds per square inch OR 1 kilogram per square centimeter ID: 342738
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Slide1Slide2
Air Pressure
Defined as the force exerted on you by the weight of tiny air
particles
in
the atmosphere per unit area.
Earth’s atmospheric pressure = 14.7 pounds per square inch OR 1 kilogram per square centimeterSlide3Slide4Slide5Slide6
Mercury
Barometer
I
nvented
by Evangelista
Toricelli
(early 1600s). First scientist to use mercury barometer to measure atmospheric pressure changes.
Inverted glass tube filled with mercury placed in a dish of mercury.
Mercury will flow from the tube to the dish until the weight of mercury is equivalent to the air pressure on the mercury dish.
29.92 in Hg = 760 mm HgSlide7Slide8Slide9
Aneroid Barometer
I
nvented
by Lucien
Vidie
(1843). “Aneroid” means
fluidless
. Registers the change in shape of a metal capsule (expanding and contracting) to measure atmospheric pressure.Slide10
Air Pressure
Millibars
comes from the original term for pressure "bar". Bar is from the Greek "
báros
" meaning weight.
29.92 in Hg = 1013.25
mb
(
millibars
) <<< Average Sea Level PressureSlide11Slide12
High Pressure
Isobar readings increase towards an area.
Winds move clockwise (anticyclone).
Fair weather conditions – no precipitation.Slide13
Low Pressure
Isobar readings decrease toward an area.
Winds move counter clockwise (cyclone)
Bad weather conditions – precipitation.Slide14
Air Pressure Systems
Isobars – lines on a map that show equal air pressure.
Recorded in
millibars
(
mb
).
Air pressure will change due to changes in air temperature
and
humidity
.
Wind blows from High Pressure systems to Low pressure systems.Slide15Slide16Slide17Slide18Slide19Slide20Slide21Slide22Slide23Slide24Slide25
Pressure Gradient Force (PGF)
Lines that are close together indicate a strong pressure gradient force – High winds.
Lines that are far apart indicate a weak pressure gradient force – Light winds.
WINDS ALWAYS BLOW FROM HIGH PRESSURE TO LOW PRESSURE.Slide26Slide27Slide28Slide29
weak
strong
weak
strongSlide30