1. Richard B. Rood (Room 2525, SRB)
AOSS 401 Geophysical Fluid Dynamics: Atmospheric Dynamics Prepared: Climate, Weather, Geography, Earth / Thermal Wind
Richard B. Rood (Room 2525, SRB)
Cell:

2. Class News Ctools site (AOSS 401 001 F13)
First Examination on October 22, 2013
Second Examination on December 10, 2013
Homework posted:
Ctools Assignments tab
Due Thursday October 10, 2013
Derivations (using notes)

3. Weather National Weather Service Weather Underground
Model forecasts:
Weather Underground
NCAR Research Applications Program

4. Outline Tour of the Earth Thermal wind Revisit the Tour of the Earth
Geography
Planet
Physics
Thermal wind
Revisit the Tour of the Earth
Vertical structure

5. Building the Radiative Balance
Redistribution by atmosphere, ocean, etc. RS
Top of Atmosphere / Edge of Space
1) The absorbed solar energy is converted to terrestrial thermal energy.
2) Then it is redistributed by the atmosphere, ocean, land, ice, life.
CLOUD
ATMOSPHERE
SURFACE

6. Another important consideration
Latitudinal dependence of heating and cooling
Top of Atmosphere / Edge of Space
After the redistribution of energy, the emission of infrared radiation from the Earth is ~ equal from all latitudes.
CLOUD
ATMOSPHERE
Because of tilt of Earth, Solar Radiation is absorbed preferentially at the Equator (low latitudes).
SURFACE
South Pole
(Cooling)
Equator
(On average heating)
North Pole
(Cooling)

7. Transfer of heat north and south is an important element of the climate at the Earth’s surface
Redistribution by atmosphere, ocean, etc.
Top of Atmosphere / Edge of Space
This predisposition for parts of the globe to be warm and parts of the globe to be cold means that measuring global warming is difficult. Some parts of the world could, in fact, get cooler because this warm and cool pattern could be changed.
CLOUD
ATMOSPHERE
heat is moved to poles
cool is moved towards equator
cool is moved towards equator
SURFACE
This is a transfer. Both ocean and atmosphere are important!

8. Scientific Method
What follows are a series of pictures, plots, graphs – mostly of observations. As we go through them think first
How do I describe the picture?
What type of behavior might be represented? Patterns, correlations
How might I investigate this behavior?
Scientific investigation is based first on observations.
What is actually in the figure? What do I know? What do I think I know? What do I want to know? What do I believe versus what do I know? What do I want to believe? What is the relation with other knowledge not represented in this particular figure.

10. Long as I remember the rain been comin’ down
[from the National Atlas (1970)]
( )
Grange, October 2006

11. Ocean Surface Currents (From Steven Dutch, U Wisconsin, Green Bay)
Good Material at National Earth Science Teachers Association

12. The Thermohaline Circulation (THC) (Global, organized circulation in the ocean) (The “conveyer belt”, “rivers” within the ocean)
Blue shading, low salt
Green shading, high salt
Where there is localized exchange of water between the surface and the deep ocean (convection)
Warm, surface currents.
Cold, bottom currents.

13. Transfer of heat north and south is an important element of the climate at the Earth’s surface.
Redistribution by atmosphere, ocean, etc.
Top of Atmosphere / Edge of Space
Large scale weather systems transport large quantities of thermal energy from equator toward the poles
CLOUD
ATMOSPHERE
heat is moved to poles
cool air moved towards equator
cool air moved towards equator
SURFACE
This is a transfer. Both ocean and atmosphere are important!

14. Tropospheric Mean Meridional Circulation
This is not exactly physical, but is a common conceptual model.

15. Dynamic atmosphere: Hurricanes --- Vortices
Satellite image
Storm that originates over warm ocean water
Scale of the motion:1000 km

16. Hurricanes and heat Sea Surface Temperature (blue cool / warm orange)

17. Hurricanes and heat

18. Mid-latitude cyclones - waves

19. Mid-latitude cyclones & Heat

20. What goes on vertically?

21. Some basics of the atmosphere
Troposphere
~ 2
Mountain
Troposphere
~ 1.6 x 10-3
Earth radius
Troposphere: depth ~ 1.0 x 104 m
This scale analysis tells us that the troposphere is thin relative to the size of the Earth and that mountains extend half way through the troposphere.

22. An estimate of the January mean temperature
note where the horizontal temperature gradients are large
mesosphere
stratopause
stratosphere
tropopause
troposphere
south
summer
north
winter

23. An estimate of the January mean zonal wind
note the jet streams
south
summer
north
winter

24. An estimate of the July mean zonal wind
note the jet streams
south
winter
north
summer

25. Let’s spend some time with the atmosphere.
Start with a typical upper tropospheric chart.
What is a good estimate of the pressure at the surface?
What is a good estimate of the pressure in the upper troposphere?
How could you figure out the geometric height?

26. Geostrophic wind 300 hPa
How does this example relate to global scales?

27. 300 hPa

28. Geopotential contours at 300 hPA
Northern Hemisphere
September 17, 2008

29. Wind and geopotential 200 hPa
Note: Variability in east-west of the wind field.
Note: Time variability of the wind field.
Note: Troughs associated with mountain ranges, continents

30. Geopotential contours at 850 hPa
Northern Hemisphere
September 17, 2008

31. 700 hPa

32. 500 hPa

33. 300 hPa

34. 50 hPa

35. North-south / Winter-summer

36. DJF 500 hPa Average

37. JJA 500 hPa Average

38. Anomaly 100 hPa

39. 23 October 2006, Geopotential Height

40. 23 October 2006, Ozone

41. The thermal wind
Connecting horizontal temperature structure to vertical wind structure in a balanced atmosphere

42. Equations of motion in pressure coordinates (plus hydrostatic and equation of state)

43. Geostrophic wind

44. Hydrostatic Balance

45. Schematic of thermal wind.
Thickness of layers related to temperature. Causing a tilt of the pressure surfaces.
from Brad Muller

46. What is a tactic for exploring vertical behavior?

47. Geostrophic wind Take derivative wrt p.
Links horizontal temperature gradient
with vertical wind gradient.

48. Thermal wind
p is an independent variable, a coordinate. Hence, x and y derivatives are taken with p constant.

49. A excursion to the atmosphere. Zonal mean temperature - Jan
approximate tropopause
south (summer)
north (winter)

50. A excursion to the atmosphere. Zonal mean temperature - Jan
∂T/∂y ?
south (summer)
north (winter)

51. A excursion to the atmosphere. Zonal mean temperature - Jan
∂T/∂y ?
<0
<0
<0
<0
>0
<0
south (summer)
north (winter)

52. A excursion to the atmosphere. Zonal mean temperature - Jan
∂T/∂y ?
∂ug/∂p ?
<0
>0
<0
<0
>0
<0
<0
<0
> 0
>0
>0
<0
south (summer)
north (winter)

53. A excursion to the atmosphere. Zonal mean wind - Jan
south (summer)
north (winter)

54. Relation between zonal mean temperature and wind is strong
This is a good diagnostic – an excellent check of consistency of temperature and winds observations.
We see the presence of jet streams in the east-west direction, which are persistent on seasonal time scales.
Is this true in the tropics?

55. Thermal wind

56. Thermal wind

57. Thermal wind

58. Thermal wind ?

59. From Previous Lecture Thickness
Note link of thermodynamic variables, and similarity to scale heights calculated in idealized atmospheres
Z2-Z1 = ZT ≡ Thickness - is proportional to temperature is often used in weather forecasting to determine, for instance, the rain-snow transition.

60. Similarity of the equations
There is clearly a relationship between thermal wind and thickness.

61. Schematic of thermal wind.
Thickness of layers related to temperature. Causing a tilt of the pressure surfaces.
from Brad Muller

62. Another excursion into the atmosphere.
850 hPa surface
300 hPa surface
from Brad Muller

63. Another excursion into the atmosphere.
850 hPa surface
300 hPa surface
from Brad Muller

64. Another excursion into the atmosphere.
850 hPa surface
300 hPa surface
from Brad Muller

65. Another excursion into the atmosphere.
850 hPa surface
300 hPa surface
from Brad Muller

66. Summary of Key Points
The weather and climate of the Earth are responses to basic attributes (geometry) of energy sources.
The patterns of weather and climate that we see are not random or accidental.
Basic redistribution of energy
Determined by characteristics of Earth – especially relation of Earth to Sun and rotation
Determined by geography
Determined by surface energy characteristics
Dynamics of atmosphere and ocean, though complex, organize the air and water into features that we can characterize quantitatively  and predict
There is strong consistency between energy, thermodynamic variables, and motion (momentum)