1. Circulation in the atmosphere

2. Balance of forces in the fluid motion
Forces due to planetary rotation
Centrifugal force  Geoid
Coriolis force  Deflection of moving fluid
Pressure gradient force
From high to low pressure

3. _ + Deflection of air flow due to Coriolis force Low Pressure
Surfaces of
constant pressure
y (latitude)
x (longitude) +
High Pressure

4. Balanced flow: geostrophic balance
Fpressure
Low Pressure
High Pressure
FCoriolis
Coriolis force 90 degrees to the right
Pressure force down the gradient
Air flows along the line of constant pressure
Particles will have the high pressure on their right (opposite in the southern hemisphere)

5. Geostrophic circulation
What would be the direction of (1) the pressure force and (2) the Coriolis force in geostrophic balance?
What would be the direction of geostrophic flow? L H
Cyclonic
Anti-cyclonic

6. Geostrophic circulation
Now we are in the Southern Hemisphere, what would be the direction of the geostrophic flow? L H
Cyclonic
Anti-cyclonic

7. H H L H H Tropical cyclone: an intense low pressure system
Air circulates around the low pressure

8. Flow under radial pressure gradient
A bucket full of water
Open up a hole in the middle
Generates a low pressure
What would happen to the water?
Non-rotating
Rotating

9. Tropical cyclones Coriolis effect Air flows around the low pressure
counter-clockwise
Energy source
Warm, moist air from tropical ocean

11. Storm surge Graphic illustration by National Hurricane Center

12. Atmosphere-ocean interaction
What are the ways that the Earth’s atmosphere and ocean interact?

13. Wind-driven ocean currents
Atmospheric winds applies frictional force on the surface waters
 Ocean waves
Wind-driven circulation
(next week)

14. Water cycle
Implications to the salinity of seawater?

15. Temperature ITCZ Salinity Subtropics Warm SST, low SSS
Excess precipitation
Salinity
Subtropics
Warm SST, high SSS
Excess evaporation
Sea surface temperature and salinity are controlled by air-sea interaction

16. 4 components of air-sea heat flux
Incoming shortwave radiation
Latitudes, cloud cover
Outgoing longwave radiation
Temperature, water vapor, cloud cover
Sensible heat flux
Boundary layer turbulence
Latent heat flux
Evaporation

17. Shortwave radiation Climatology
Average over long time period ( )
Upward positive (positive into the atmosphere)

18. Factors controlling SW radiation
Latitude
Cloudines (albedo)

19. Longwave radiation Climatology (1968-1996)
Upward positive (positive into the atmosphere)

20. Longwave radiation
SST, cloud and water vapor

21. Sensible heat flux Climatology (1968-1996)
Upward positive (positive into the atmosphere)
Turbulent heat exchange between ocean and atmosphere

22. Sensible heat flux
Driven by surface wind speed and air-sea temperature difference
Ch = 0.83e-3 for stable condition
Ch = 1.10e-3 for unstable condition

23. Latent heat flux Climatology (1968-1996)
Upward positive (positive into the atmosphere)
Proportional to the rate of evaporation

24. Latent heat flux Rate of evaporation
- Wind speed and relative humidity

25. Net heat flux Climatology (1968-1996)
Upward positive (positive into the atmosphere)

26. Ocean heat transport Ocean gains heat from the atmosphere in tropics
Ocean circulation transports heat poleward, and release back to the atmosphere at high latitudes

27. Biogeochemical cycle
(in October after midterm)