1. ATOC 4720 class38
Thermally driven circulation in the absence of rotation
Generation of kinetic energy

2. In the previous class: Primitive equations:( )

3. 1. Thermally driven circulation without rotation (f=0)
Lab experiment 1:
Energetics: available potential energy

4. Energetics for large scale atmospheric circulation (f=0)
Available potential energy Kinetic energy;
m=1
Fluid motion.
Assume no friction, what will happen?

5. Oscillate forever because of E
With friction: equilibrium state -- state of rest
Random molecular
motions
Potential energy(PE) Kinetic energy internal energy
Analagous to atmosphere: symmetric ITCZ;
Question: Why do atmosphere is in quai-steady
Motion, rather than a state of rest?

6. Experiment 2: A steady-state
Answer: In real atmopshere, available potential energy is
constantly replenished by diabatic heating
Experiment 2: A steady-state
HEAT Sink
HEAT Source

7. N pole
Minimum (net loose: sink)
Solar radiation maximum (earth surfacenet gain: source) EQ
Minimum (net loose: sink)
S pole

8. Net+Latent heat EQ
Pole
Atmosphere: potential temperature rather than temperature
Once motion starts: rate of available PE = dissipation
Use primitive equations for explanation.

9. 2. Generation of kinetic energy (f=0)
Pressure surfaces
PE -- KE(Kinetic energy) : work done by PGF

10. Type (a): thermally direct; Type (b): thermally indirect
Ignore other horizontal forces and f=0 (CF=0):
Work done for unit mass unit time
Type (a): thermally direct;
Type (b): thermally indirect

11. Convergence
Divergence
Z-coordinate: If