1. Energy and Heat Transfer
AOS 101 Section Feb

2. Heat, Temperature, and Energy Transfer
Some basic definitions:
Temperature – Related to the energy content of an object. In a gas, the temperature is defined as the average kinetic energy of the gas particles.

3. Heat, Temperature, and Energy Transfer
Some basic definitions:
Heat – Related to the energy transfer between two objects. Heat is the transfer of energy from a warm object to a cool object, obeying the 2nd Law of Thermodynamics: “Things fall apart”

4. Heat, Temperature, and Energy Transfer
Important Note: Temperature =/= Heat
You cannot “feel” the temperature of an object, only the heat exchange between yourself and that object. It is related to the object’s temperature, but not the same thing.

5. HOT
COLD
Temp

6. ENERGY
TRANSFER
HOT
COLD
Temp

7. ROOM
TEMP
ROOM
TEMP
Temp

8. More Terms to Know
Specific Heat Capacity – This is the ratio of the amount of energy 1 Kg of a substance requires in order to change its temperature by 1 Kelvin: Q C = T
C = Specific Heat Capacity
Q = Energy (J)
Δ T = Change in Temperature (K)

9. Some Sample Specific Heat Capacities:
Air
1.0035
Water
4.1813
Diamond
0.5091
Glass
0.8400
Ice
2.050
Aluminum
0.897
Helium
5.1932

10. Kinds of Energy Transfer
There are four kinds of energy transfer:
Conduction
Convection
Advection
Radiation

11. Kinds of Energy Transfer
There are four kinds of energy transfer:
Conduction
Convection
Advection
Radiation
Conduction, Convection, and Advection require some kind of medium to act through – Radiation does not.

12. Kinds of Energy Transfer
There are four kinds of energy transfer:
Conduction
Convection
Advection
Radiation
Air is a poor conductor of heat, therefore Convection, Advection, and Radiation all play large roles in the atmosphere, while Conduction is less important.

13. Kinds of Energy Transfer
Advection
Energy can be transferred from one region to another through the transport of warm or cool air from one place to another – Advection of temperature
Cyclones are especially good at this:

15. L Cool air from the pole is being advected to the south
Warm air from the tropics is being advected to the north

16. L Uniformly cold near the pole
Strong temperature contrast exists along a narrow line
Uniformly warm in the tropics

17. L Uniformly cold near the pole Warm Front Cold Front
Uniformly warm in the tropics

18. L L L L

19. L L L L
“Wave Train”

20. Kinds of Energy Transfer
Convection
Energy can be transferred when a fluid is forced to vertically mix, allowing hot and cold portions of the fluid to make contact and even the temperature out
“Hot air rises and cold air sinks”

21. Convection
In the atmosphere, convection occurs when relatively warm air is below relatively cool air, forcing the warm air to rise and cold air to sink – “overturning”
Overturning can occur by warming the air at the surface OR cooling the air above

22. Lake Effect Snow

23. Lake Effect Snow
“Lake effect” snow is a form of convection which occurs when very cold air passes over relatively warm water:
Cold
Warm N S

24. Cold air from the land is advected over the warm water surface
Lake Effect Snow
“Lake effect” snow is a form of convection which occurs when very cold air passes over relatively warm water:
Cold air from the land is advected over the warm water surface
Cold
Warm N S

25. Warm air is now underneath cold air, leading to convective overturning
Lake Effect Snow
“Lake effect” snow is a form of convection which occurs when very cold air passes over relatively warm water:
Warm air is now underneath cold air, leading to convective overturning
Cold
Warm
Cold N S

26. Lake Effect Snow
“Lake effect” snow is a form of convection which occurs when very cold air passes over relatively warm water:
Rising warm air creates strong convective clouds and snow – “Lake Effect” snow
Cold N S

27. Videos of Convection Convection Video 1
Convection Video 2
Convection Video 3

28. Kinds of Energy Transfer
Radiation
Energy can be transmitted from one object to another through emission and absorption of electro-magnetic waves
The Earth-Atmosphere-Sun system is the most important aspect of this kind of energy transfer for meteorology

29. Earth-Atmosphere-Sun System

30. Earth-Atmosphere-Sun System
Sun is at ~6000 K, and emits shortwave radiation to the atmosphere
Sun
Earth
Atmosphere

31. Earth-Atmosphere-Sun System
Atmosphere is selectively transparent to solar radiation, allowing it to pass through to the Earth, where it is absorbed
Sun
Earth
Atmosphere

32. Earth-Atmosphere-Sun System
Earth heats up and emits longwave radiation outward, some of which is selectively absorbed by the atmosphere, also heating the atmosphere (the rest escapes to space)
Sun
Earth
Atmosphere

33. Earth-Atmosphere-Sun System
Atmosphere heats up and emits longwave radiation both toward the Earth, and away from the Earth into space
Sun
Earth
Atmosphere

34. Earth-Atmosphere-Sun System
Earth has TWO sources of radiation heating the surface: the Sun AND the atmosphere. This is why the Earth is warmer than 0oF
Sun
Earth
Atmosphere

35. Earth-Atmosphere-Sun System
The more longwave radiation the atmosphere absorbs from the Earth, the more longwave radiation is radiated back to Earth – “Greenhouse Effect”
Sun
Earth
Atmosphere

36. Radiation In general, when radiation strikes an object, it can be:

37. Radiation In general, when radiation strikes an object, it can be:
Transmitted – radiation passes through the object without being absorbed

38. Radiation In general, when radiation strikes an object, it can be:
Transmitted – radiation passes through the object without being absorbed
Absorbed – radiation is retained by the object and stored energy is manifest as an increase in temp.

39. Radiation In general, when radiation strikes an object, it can be:
Reflected – radiation bounces off of object and travels in a new direction
Transmitted – radiation passes through the object without being absorbed
Absorbed – radiation is retained by the object and stored energy is manifest as an increase in temp.

40. Radiation In general, when radiation strikes an object, it can be:
Reflected – radiation bounces off of object and travels in a new direction
Transmitted – radiation passes through the object without being absorbed
Absorbed – radiation is retained by the object and stored energy is manifest as an increase in temp.
Scattered – radiation strikes a small object and reflects in all directions (though not necessarily equally)

41. Rtotal=Rtrans+Rabs+Rref+Rscat
Radiation
When radiation strikes an object, it MUST do one or more of these things. There is no radiation that is not transmitted, absorbed, reflected, or scattered:
Rtotal=Rtrans+Rabs+Rref+Rscat
Reflected – radiation bounces off of object and travels in a new direction
Transmitted – radiation passes through the object without being absorbed
Absorbed – radiation is retained by the object and stored energy is manifest as an increase in temp.
Scattered – radiation strikes a small object and reflects in all directions (though not necessarily equally)

42. What About Latent Heat?
Technically, there are five forms of energy transfer to consider:
Conduction
Convection
Radiation
Advection

43. What About Latent Heat?
Technically, there are five forms of energy transfer to consider:
Conduction
Convection
Radiation
Advection
Latent Heat

44. What About Latent Heat?
Technically, there are five forms of energy transfer to consider:
Conduction
Convection
“Sensible Heat”
Radiation
Advection
Latent Heat

45. What About Latent Heat?
“Sensible Heat” – Energy transfer via the manipulation of temperature – an object becoming warmer or colder due to the absorption or emission of thermal energy. Heat transfer you can sense.
Latent Heat – Energy transfer via the manipulation of the phase state of water. Heat transfer latent to the state of water.

46. Heating Ice Into Water Vapor
Temp
Energy supplied to ice causes ice to increase in temperature – sensible heat
Time

47. Heating Ice Into Water Vapor
Temp
Ice reaches melting point, and supplied energy now forces ice to melt – absorbing latent heat
Time

48. Heating Ice Into Water Vapor
Ice has completely melted into water, and now supplied heat increases water temperature – sensible heat
Temp
Time

49. Heating Ice Into Water Vapor
Temp
Water reaches boiling point and uses supplied energy to convert to water vapor – absorbing latent heat
Time

50. Heating Ice Into Water Vapor
Temp
Water boils completely, and supplied energy now increases temperature of water vapor – sensible heat
Time

51. Sensible heat transfer Sensible heat transfer Sensible heat transfer
Heating Ice Into Water Vapor
Sensible heat transfer
Sensible heat transfer
Sensible heat transfer
Temp
Latent heat transfer
Latent heat transfer
Time