How differences in pressure causethe atmosphere (or ocean) to move

Dr. Rob BlackMeteorology Professor

Georgia Tech

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/

2) Monsoon (in India)

The Telegraph NC State University

http://www.telegraph.co.uk/ http://www.nc-climate.ncsu.edu/edu/k12/.Monsoons

3) Afternoon rain in Paradise

dreamstime.com http://www.dreamstime.com/

What do we need to know?

1) Unequal heating of Earth’s Surface:

http://sharegeography.co.uk/

What do we need to know?

2) Fluid parcels: Blobs of air or water

What do we need to know?

3) Heat a fluid parcel -> What happens:

Size? Density?

Movement?

Process?

Increases Decreases

Rises Up

Convection

What do we need to know?

4) Pressure: “Pushing” of nearby parcels

What do we need to know?

5) Fluid parcels move from regions of high pressure toward low pressure

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)

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)

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

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

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!

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?