How differences in pressure cause the atmosphere (or ocean) to move Dr. Rob Black
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How differences in pressure causethe atmosphere (or ocean) to move
Dr. Rob BlackMeteorology Professor
Georgia Tech
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What are we trying to understand?
1) Sea Breeze (at the beach)
Millersville University NOAA Jet Stream
http://www.atmos.millersville.edu/~lead/SeaBreezeYard.jpg
http://oceanservice.noaa.gov/education/yos/resource/JetStream/
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2) Monsoon (in India)
The Telegraph NC State University
http://www.telegraph.co.uk/ http://www.nc-climate.ncsu.edu/edu/k12/.Monsoons
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What do we need to know?
1) Unequal heating of Earth’s Surface:
http://sharegeography.co.uk/
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What do we need to know?
2) Fluid parcels: Blobs of air or water
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What do we need to know?
3) Heat a fluid parcel -> What happens:
Size? Density?
Movement?
Process?
Increases Decreases
Rises Up
Convection
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What do we need to know?
4) Pressure: “Pushing” of nearby parcels
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What do we need to know?
5) Fluid parcels move from regions of high pressure toward low pressure
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Let’s now consider an experiment!!
Locally heat bottom of bowl of water:
1: Flame heats bowl (by radiation)2: Bowl heats water (by conduction)
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Let’s now consider an experiment!!
Try to predict what will happen in bowl:
Q1: What will happen to hot blob of water?
Size?
Density?
Movement?
Increase
Decrease
Rise upward(Convection)
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Let’s now consider an experiment!!
Hot water blob now pushes upward:
Q2: How does pressure change above/below?
At top?
At bottom?
Increases
Decreases
H
L
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Let’s now consider an experiment!!
“Close the loop” on what will happen:
Q3: How will water move at top and bottom?
At top?
At sides?
At bottom?
Spread out(Diverge)
Sinking
Move Inward(Converge)
H
L
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Experimental Instructions
♠ Place a drop of blue food color at one side
♥ Place a drop of red food color at opposite side
♣ Drops will first sink and then mix with water
♦ Mixed drops will then show motion in water
♠ Look for area where water is rising
♥ Place a drop of green food color in rising water
♣ Watch what happens!
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Experimental Observations
♠ Where does water appear to rise or sink?
♥ Where does water spread out (diverge)?
♣ Where does water move together (converge)?
♦ How do your observations compare with your expectations (based upon physical principles presented in the powerpoint)?
♠ How are the 2 experiments different or similar?
♥ How do the experiments compare to sea breeze, etc?