RADIATION CHARACTERISTICS

1. RADIATION CHARACTERISTICS

2. OUR ENERGY SOURCE

3. RADIATION What happens to solar energy ? 1. Absorption (absorptivity=) Results in conduction, convection and long-wave emission 2. Transmission (transmissivity=) 3. Reflection (reflectivity=)  +  +  = 1

4. Response varies with the surface type Snow reflects 40 to 95% of solar energy and requires a phase change to increase above 0°C Forests and oceans absorb more than dry lands Then why do dry lands still “heat up” more? Oceans transmit solar energy and have a high heat capacity

5. Characteristics of Radiation Energy due to rapid oscillations of electromagnetic fields, transferred by photons The energy of a photon is equal to Planck’s constant, multiplied by the speed of light, divided by the wavelength All bodies above 0 K emit radiation Black body emits maximum possible radiation per unit area. Emissivity,  = 1.0 All bodies have an emissivity between 0 and 1 E = hv 

7. Stefan-Boltzmann Law As the temperature of an object increases, more radiation is emitted each second

8. Temperature determines E,  emitted Higher frequencies (shorter wavelengths) are emitted from bodies at a higher temperature Max Planck determined a characteristic emission curve whose shape is retained for radiation at 6000 K (Sun) and 300 K (Earth) Energy emitted = (T0)4 Radiant flux or flux density refers to the rate of flow of radiation per unit area (eg., Wm-2) Irradiance = incident radiant flux density Emittance = emitted radiant flux density

9. Wien’s Displacement Law As the temperature of a body increases, so does the total energy and the proportion of shorter wavelengths max = (2.88 x 10-3)/(T0) *wavelength in metres Sun’s max = 0.48 m Ultraviolet to infrared - 99% short-wave (0.15 to 3.0 m) Earth’s max = 10 m Infrared - 99% longwave (3.0 to 100 m)

10. Terrestrial radiation Solar radiation

13. SELECTIVE ABSORPTION

14. 8-11 m window

15. ALBEDO: April, 2002 White and red are high albedo, green and yellow are low albedo

17. SURFACE ALBEDO • white snow 0.80-0.95 • old snow 0.40-0.60 • vegetation 0.15-0.30 • light colour soil 0.25-0.40 • dark colour soil 0.10 • clouds 0.50-0.90 • calm water 0.10 (noon) March 3, 2009

19. Radiation Balance DAYTIME: Q* = K - K + L - L Q* = K* + L* NIGHT: Q* = L* K = solar (shortwave) radiation ↓ = incoming L = longwave (terrestrial radiation) ↑ = outgoing Q* = net all-wave radiation * = net

21. L Source: NOAA

22. MECHANISMS OF HEAT TRANSFER

23. Conduction The transfer of heat from molecule to molecule within a substance

24. Convection and Thermals

25. Convection The transfer of heat by the mass movement of a substance (eg. air) Sinking air is compressed and warms Rising air expands and cools

26. THE IMPORTANCE OF LATENT HEAT

27. The Hydrological Cycle

29. Heat capacity The amount of heat energy absorbed (or released) by unit volume of a substance for a corresponding temperature rise (or fall) of 1 °C Specific heat The amount of heat energy absorbed (or released) by unit mass of a substance for a corresponding temperature rise (or fall) of 1 °C

30. Latent heat The heat energy required to change a substance from one state to another Sensible heat Heat energy that we can feel and sense with a thermometer

31. Radiation Sensors (PAR and K) Raingauge Thermometer and radiation shield SENSIBLE HEAT Datalogger Photo: Weather station, Tausa, Cundinamarca, Colombia (3,243 m asl)

32. THE CAUSE OF SEASONALITY

38. WHERE DOES THE SUN RISE?

39. Check this out: http://www.jgiesen.de/sunshine/index.htm

40. WHEN IS THE HOTTEST PART OF THE DAY?

46. Local effects of radiation distribution N

48. Air Temperature Dec 15, 2004 Jan 19, 2005 Temperature (C)

49. Soil Temperature Dec 15, 2004 Jan 19, 2005 Temperature (C)

50. Dewpoint Temperature Dec 15, 2004 Jan 19, 2005 Snowcover Temperature (C)