Atmospheric Radiation GCC Summer School Montreal - August 7, 2003

1. Atmospheric RadiationGCC Summer SchoolMontreal - August 7, 2003 Glen Lesins Department of Physics and Atmospheric Science Dalhousie University Halifax glen.lesins@dal.ca

2. Outline • Introductory concepts • Radiation and Climate • Radiative Transfer Theory • Remote Sensing

3. Credits • K.N. Liou, An Introduction to Atmospheric Radiation, 2nd Ed., 2002 • Web Lecture Notes by Prof. Irina Sokolik, http://irina.colorado.edu/teaching.htm

4. Global Annual Energy Balance Kiehl and Trenberth (1997); IPCC (2001)

6. What is the Solar Constant? • 1366 W m-2 • How constant? • Earth’s orbit and tilt (annual) • Sunspot cycle (11 years) • Longer time variations

7. Solar Irradiance Variation from ACRIM

8. http://science.nasa.gov/headlines/images/sunbathing/sunspectrum.htmhttp://science.nasa.gov/headlines/images/sunbathing/sunspectrum.htm

9. Solar vs. Terrestrial Radiation

10. Absorption of Radiation by Gases 1. Ionization/Dissociation - UV 2. Electronic Transition - UV 3. Vibrational/Rotational Transition - Visible/IR 4. Pure Rotational - IR

11. Transmission through the Atmosphere Terrestrial Solar IR Window

12. Radiative Interactions - Dipole Transitions

13. Vibrational Modes

14. – + + – •• •• •• O O O O O O •• •• •• •• •• •• •• •• •• Ozone (O3) Electrostatic potentialmap shows both endoxygens are equivalentwith respect to negativecharge. Middle atomis positive. www.facstaff.oglethorpe.edu/mwolf/PowerPoint/ CareyOrgPP/sections1st/Chapter%201bx.ppt

15. Absorption by Gases

17. Solar Irradiance

18. Particle Size Wavelength Scattering of Radiation Size Parameter, a a = 2pr/l

19. Rayleigh Scattering http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html#c2

20. Mie Theory for mr=1.5

21. Normalized Phase Functions From Mie Theory

22. Global Annual Energy Balance Kiehl and Trenberth (1997); IPCC (2001)

23. Zonal Average Irradiance Solar Terrestrial Net Meridional Transport

24. Cloud Radiative Forcing from ERBE

25. Radiative Equilibrium & Role of Convection

26. Solar Heating Rates from Model

27. Zonal Annual Average from Satellite

28. Results from SOCRATES (2-D Radiative-Chemical) http://acd.ucar.edu/models/SOCRATES/socrates/socrates1.html http://acd.ucar.edu/models/SOCRATES/socrates/socrates1.html

29. Annual Mean Net Radiation Flux from Surface Based Measurements

30. Terrestrial IR Spectra

31. Modelled IR Fluxes

34. Global mean radiative forcing of the climate system for the year 2000, relative to 1750 3 Halocarbons N O Aerosols 2 2 CH 4 Warming Black carbon from CO 1 Tropospheric 2 Aviation-induced Mineral fossil fuel Solar ozone dust burning Radiative forcing (W m-2) Contrails Cirrus 0 Stratospheric Organic ozone Land-use carbon Biomass (albedo) Cooling from Aerosol -1 burning Sulphate only fossil indirect fuel effect burning -2 High Medium Low Very Very Very Very Very Very Very Very Medium Low Low Low Low Low Low Low Low LevelofScientificUnderstanding

35. Global Annual Energy Balance Kiehl and Trenberth (1997); IPCC (2001)

36. Radiative Transfer Equation Radiance Cosine of solar zenith angle Azimuthal Angle Beer’s Law SourceFunction Optical Depth

37. Plane Parallel Radiances

38. Solution to the Radiative Transfer Equation Upward Radiance Downward Radiance

39. SUN Single & Multiple Scattering Source Source Function Multiple Scattering Term Single Scattering Term

40. Surface Reflectance

41. Bi-directional Reflectance Distribution Function (BRDF)

42. Surface Albedo

43. Remote Sensing of Clouds

44. Effect of Clouds from Radiative-Convective Model

45. Solar Albedo of Clouds - Theory

46. Indirect Aerosol Effect - ShiptracksL1B true color RGB composite (25 April 2001)

47. Effective radius retrieval (using 2.1 µm band, all phases) 60 45 re (µm) 30 15 0

48. Shiptracks from MODIS Indirect Aerosol Effect July 1, 2003

49. Global Annual Energy Balance Kiehl and Trenberth (1997); IPCC (2001)

50. IR Brightness Temperature from ER-2 (Clear)