1. The Earth’s Energy Budget/ Heat Balance

2. What is heat?

6. Main Objectives
Trace the flow of energy through the atmosphere

9. / C

10. A budget
Income = outgo
Outgo = 51
Income = 51

14. Energy Income Insolation – incoming solar radiation
Predominantly short wave radiation
(0.4 – 0.7mm)
Varies locally with season, latitude
Total annual global insolation should remain constant

15. When energy enters the atmosphere it can be ….
Absorbed(अवशोषित)
Reflected(परावर्तित)
Scattered(प्रकीर्ण)
Transmitted(प्रसारित)

17. Absorbed
Energy is absorbed by gasses, particulates, droplets Different wavelengths are absorbed differently. Ex. Most UV is absorbed by ozone, but most visible light is not absorbed CO2 and H2O are better at absorbing IR than N2 or O2

18. Absorbed
Result Absorber warms Amount of solar energy reaching the surface is reduced

19. Reflected
Specular reflection – a beam is reflected with equal intensity Diffuse radiation – a beam is split into many smaller, less intense beams = scattering

20. Rayleigh scattering Caused by individual gas molecules
Scatters shorter wavelengths (blue) more than longer wavelengths
Redirects the scattered waves in every direction (and thus toward any direction), therefore, the sky looks blue

21. Rayleigh scattering
Responsible for red sunsets

22. Mie scattering Caused by aerosols Tend to scatter all wavelengths
Tends to scatter energy forward (toward the surface of the earth)
Pollution causes the sky to look gray

23. Rayleigh and Mie scattering

24. Transmitted
Some amount of solar energy passes unobstructed to the surface of the earth Amount depends on atmospheric conditions

25. Overall annual amounts

26. When solar energy reaches the surface of the earth it can be…
Reflected
Absorbed

27. Reflected
Albedo – reflectivity. Percent of energy reflected by a material. Snow has a higher albedo than dirt Overall the albedo of the earth is about 30%

28. If solar energy is absorbed by the surface it will eventually be removed by …
Radiation
Conduction
Convection

29. The surface emits longwave radiation
ONE TO 10mm
Of this radiation some passes out into space, some is absorbed by the atmosphere and then reemitted in all directions

30. Conduction( चालन) Can warm the earth below
Can warm the laminar boundary layer (very thin layer of air in contact with the surface)

31. Convection (संवहन) Cool air sinks In the process mixing occurs
Energy is transferred by movement of material in a fluid
Warm air rises
Cool air sinks
In the process mixing occurs

32. Free convection

33. Forced convection

34. Convection Sensible heat – heat that you can sense (feel)
i.e. warm air
Latent heat – energy used to change the phase of water
Latent heat of fusion – heat required to melt ice
Latent heat of evaporation

35. Even though the energy budget of the atmosphere remains balanced there are latitudinal variations
400 to 900 net deficit
00 to 400 net surplus

36. Budget is balanced by advection – horizontal movements of energy
Global wind currents
Ocean currents

37. Energy Balance and Temperature
Chapter 3
Energy Balance and Temperature

38. Measurement of temperature - statistics
Daily mean = mean of daily high and low temp.
Monthly mean = mean of daily means for a month
Yearly mean = mean of monthly means for a year

39. Temperature controls Land and water Ocean currents Altitude
Geographic position
Cloud cover and albedo

40. Land and Water Land exchanges heat more readily than water
Water moves and thus mixes
Light can penetrate into the water
water has a high specific heat

41. Ocean currents
Ocean currents transfer heat

42. Altitude Air is heated by the surface
The farther away from the surface the cooler
Mean environmental lapse rate = 6.50C/km

43. Geographic Position Coast vs. inland
Windward vs. leeward side of mountains

44. Cloud Cover and Albedo
Cloud cover tends to reduce temperature variation (cooler days and warmer nights)
High albedo reduces warming

45. Measurement of temperature - tools
Maximum thermometer
Minimum thermometer
Thermograph
Thermisor
Instrument shelter