1. Surface Albedo and SW Flux Calculation Y-C. Zhang and W.B. Rossow LandFlux Conference CNES/CESBIO, Toulouse, France May 28 – 31, 2007

2. 2 OUTLINE I. Introduction II. Datasets Used III. SRF Albedo & SW Comparison: FD vs MODIS IV. SRF Albedo & SW Comparison: FD vs CERES V. SRF Albedo & SW Comparison: FD vs GEWEX-SRB VI. SRF Albedo & SW Comparison: FD vs SOB VII. SRF Direct/Diffuse Fluxes & Their ratio VIII. Uncertainties of Albedo and Others and their Caused Global, Daily-mean SW Uncertainties

3. 3 I. Introduction Clarifications of (Land) Surface SW Albedo and Fluxes ● Definition: (Surface) Albedo = Reflected / Incident Flux (at Surface) ● Spectral Dependence: Broadband: 0.2 – 5.0 μm ~ SW Visible: ~ 0.2 – 0.7 μm ~ VIS SW Near-Infrared: ~ 0.7 – 5.0 μm ~ NIR SW ● Scene Dependence: ♦ (1) Black-Sky Albedo (BSA, or True/Inherent Albedo) ) ~ Direct SW (2) White-Sky Albedo ~ Diffuse SW ♦ (a) Full-sky Albedo (Blue-sky Albedo; All-sky Albedo) ~ full-sky SW (b) Clear-sky Albedo: Often approximated to BSA ~ clear-sky SW ● TOA Clear-sky Albedo: Often used to check consistency with SRF albedo (BSA or SRF clear-sky albedo) or even produce SRF abedo

4. 4 Clear-sky Albedo Difference (%): TOA & SRF from FD for 0401

5. 5 Clear-sky Albedo Difference (%): TOA & SRF from FD for 0407

6. 6 II. Datasets Used 1. ISCCP-FD Flux Product (Version: 0.00) ► FD is a self-consistent and physically-integrated, SRF-to-TOA profile flux product, including all up & down, SW (diffuse/direct and VIS/NIR) and LW for full-, clear- and overcast sky Spatial resolution: horizontal: 280-km equal-area (2.5° on equator) vertical: 5 levels (SRF-680mb-440mb-100mb-TOA) Temporal resolution: 3-houly (UTC = 0, 3, … 21) Spatial coverage: fully global (on 280-km equal-area map) Temporal coverage: July 1983 → Dec. 2004 → … ► Five Datasets of the FD product: (1) FD-TOA, (2) FD-SRF, (3) FD-PRF, (4) FD-INP & (5) FD-MPF ► Radiative Model: (modified) NASA GISS model using mainly ISCCP-D1 Albedo: Land: VIS -- based on ISCCP-D1 visible reflectance NIR -- modified model ratio of VIS/NIR over 8 Vege types Ocean: from NASA GISS model

7. 7... II. Datasets Used 2. MODIS Surface Albedo (and Flux) Product ► Version: MOD43C2 V004 L3 (from Crystal Schaaf) ► Black Sky Albedo Spatial resolution: 0.05 ° X 0.05° (Averaged to 280 km equal area) Temporal resolution: 16-day (orbital double repeat cycle; New 8-day?) Spatial coverage: global (usually not fully) Spectral Features: VIS 0.3 – 0.7 μm (based on 3 channels) NIR 0.7 – 5.0 μm (based on 4 channels) ► SW Flux (MODIS-FD) Calculation is based on MODIS BSA using ISCCP-FD production code

8. 8... II. Datasets Used 3. CERES Flux Product ► Version: SRBAVG Ed. 2 Rv. 1 from GEWEX-RFA website ► Satellite: TERRA FM1 or FM2, XTRK and GEO-interpolated ► SRF and TOA up & down, SW and LW for all and clear sky Spatial resolution: horizontal: 2.5° X 2.5° Temporal resolution: monthly mean (based on original 3-hourly CERES) Spatial coverage: fully global Temporal coverage: March 2000 → ► Radiative Model for SRF fluxes: Model B: LPSA/LPLA (Langley Parameterized SW/LW Algorithm) based on the relationships with TOA fluxes and atmospheric data

9. 9... II. Datasets Used 4. GEWEX-SRB Flux Product ► Version: SW Rel 2.5 and LW Rel 2.6 (from Paul Stackhouse) ► SRF and TOA up & down, SW and LW for all- and clear sky Spatial resolution: 1° X 1° (Averaged to 280 km equal area) Temporal resolution: 3-houly (UTC = 0, 3, … 21) Spatial coverage: fully global Temporal coverage: July 1983 → Dec. 2004 ► Radiative Model: SW (0.2 – 4.0 μm) from Pinker/Laszlo (quality check by Staylor Model) LW (4.5 – ∞ μm) from Fu/Liou, (quality check by Gupta Model)

10. 10... II. Datasets Used 5. SOB = Surface Station Observed Flux Product, available at GEWEX-RFA project. ► Based on 15 selected stations of BSRN, ARM and SURFRAD networks obtained from GEWEX-RFA (Processed by Chuck Long) ► SRF down and up, SW (diffuse and direct) and LW and their inferred clear-sky fluxes, cloud fraction, etc. Temporal resolution: 15-minute (from original 1-3 min) (Averaged to 8 Local Solar time or daily/monthly mean) Temporal coverage: 2004 for 15-min 1992-2004 for monthly-mean 15-min ► Processing method: “Next Generation Flux Analysis” (NGFA) method

11. 11... II. Datasets Used 6. References (only one for each dataset is given below) (1) ISCCP-FD: Zhang, Y-C., W.B. Rossow, A.A. Lacis, V. Oinas and M.I. Mishchenko (2004), Calculation of radiative fluxes from the surface to top-of-atmosphere based on ISCCP and other global datasets: Refinements of the radiative transfer model and the input data, J. Geophys. Res., 109, D19105, doi:10.1029/2003JD004457. (2) MODIS: Schaaf, C.B., et al. (2002), First operational BRDF, albedo and nadir reflectance products from MODIS, remote sens. Environ., 83, 135-148. (3) CERES: Loeb, N.G., B.A. Wielicki, W. Su, K. Loukachine, W. Sun, T. Wong, K.J. Priestley, G. Matthews, W.F. Miller, and R. Davies (2007), Multi-Instrument Comparison of Top-of-Atmosphere Reflected Solar Radiation, J. Clim., 20, 575-591.

12. 12... II. Datasets Used … 6. References (4) GEWEX-SRB: Stackhouse Jr., P.W., S. J. Cox, S.K. Gupta, M.Chiacchio, and J.C., Mikovitz (2001), The WCRP/GEWEX surface radiation budget project release 2: An assessment of surface fluxes at 1 degree resolution. International Radiation Sysposium, St.-Petersburg, Russia, July 24-29, 2000. IRS 2000: Current Problems in Atmospheric Radiation, W.L. Smith and Y. Timofeyev (eds.), A. Deepak Publishing, 147. (5) SOB: Long, C.N. (2004), The next generation flux analysis: Adding clear-sky LW and LW cloud effects, cloud optical depths, and improved sky cover estimates, in Proceedings of the Fourteenth ARM Science Team Meeting, Albuqueque, New Mexico, March 22-26, 2004, available at http://www.arm.gov/publications/proceedings.stm.http://www.arm.gov/publications/proceedings.stm.

13. III. SRF Albedo & SW Comparison: FD vs MODIS Land SRF BSA (%) for 4 16-day periods (2000 4/6, 7/11 & 9/29 and 2001 1/17)

14. 14 VIS BSA for four 16-day Period comparison: FD vs. MODIS

15. 15 NIR BSA for four 16-day Period comparison: FD vs. MODIS

16. 16 Total BSA for four 16-day Period comparison: FD vs. MODIS

17. 17 VIS BSA Difference: FD & MODIS for 16-day from 000711

18. 18 VIS BSA Difference: FD & MODIS for 16-day from 010117

19. 19 NIR BSA Difference: FD & MODIS for 16-day from 000711

20. 20 NIR BSA Difference: FD & MODIS for 16-day from 010117

21. 21 TTL BSA Difference: FD & MODIS for 16-day from 000711

22. 22 TTL BSA Difference: FD & MODIS for 16-day from 010117

23. 23 BSA-based Constructed SRF Clr-sky Albedo (%) & SW-up (w/m 2 ): FD vs. MODIS-FD for July 2000 and January 2001

24. 24 SRF Clr-sky Albedo Difference (%): FD & MODIS for July 2000

25. 25 SRF Clr-sky Albedo Difference (%): FD & MODIS for Jan. 2001

26. 26 TOA Clr-sky Albedo (%): FD vs. MODIS-FD for July 2000 & Jan. 2001: Snow-free Land

27. 27 TOA Clr-sky Albedo (%): FD vs. MODIS-FD for July 2000 & Jan. 2001: Snow-covered Land

28. 28 TOA Clr-sky SW-up (W/m 2 ): FD vs. MODIS-FD July 2000 & Jan. 2001: Snow-free Land N. Africa & Arabia Peninsula

29. 29 TOA Clr-sky SW-up (W/m 2 ): FD vs. MODIS-FD July 2000 & Jan. 2001: Snow-covered Land

30. 30 IV. SRF Albedo & SW Comparison: FD vs. CERES Averaged from 36-month (0003 to 0302) Global, monthly-mean statistics; SW in W/m 2 ; ALB in %; Cor… are without unit

31. 31.. SRF Albedo & SW Comparison: FD vs. CERES Averaged from 36-month (0003 to 0302) Land-only, monthly-mean statistics; SW in W/m 2 ; ALB in %; Cor… are without unit

32. 32 Difference of annual-mean TOA Clear-sky Albedo (%): FD - CERES (Land)

33. 33 Difference of annual-mean SRF Clear-sky Albedo (%): FD - CERES (Land)

34. 34 Difference of Annual-mean SRF Clear-sky SW↓ (W/m 2 ): FD - CERES (Land)

35. 35 Difference of Annual-mean SRF Clear-sky SW↑ (W/m 2 ): FD - CERES (Land)

36. 36 Difference of Annual-mean SRF Clear-sky SW-net (W/m 2 ): FD - CERES (Land)

37. 37 Difference of annual-mean TOA Full-sky Albedo (%): FD - CERES (Land)

38. 38 Difference of Annual-mean SRF Full-sky SW↓ (W/m 2 ): FD - CERES (Land)

39. 39 Difference of Annual-mean SRF Full-sky SW↑ (W/m 2 ): FD - CERES (Land)

40. 40 Difference of Annual-mean SRF Full-sky SW-net (W/m 2 ): FD - CERES (Land)

41. 41 Difference of Annual-mean SRF Cloud Effects of Albedo (%): FD - CERES (Land)

42. 42 Difference of Annual-mean SRF Cloud Effects (W/m 2 ): FD - CERES (Land)

43. 43 Difference of January SRF Full-sky Albedo (%): FD - CERES (Land)

44. 44 Difference of January SRF Full-sky SW-net (W/m 2 ): FD - CERES (Land)

45. 45 V. SRF Albedo & SW Comparison: FD vs GEWEX-SRB Statistics for 85-89 Annual-mean Comparison (albedo in % & flux in w/m 2 )

46. 46 85-89 Annual-mean SRF Clear-sky Albedo: FD - SRB (%)

47. 47 85-89 Annual-mean SRF Clear-sky SW↓: FD - SRB (W/m 2 )

48. 48 85-89 Annual-mean SRF Clear-sky SW↑: FD - SRB (W/m 2 )

49. 49 85-89 Annual-mean SRF SW↓: FD - SRB (W/m 2 )

50. 50 85-89 Annual-mean SRF SW↑: FD - SRB (W/m 2 )

51. 51 85-89 Annual-mean SRF SW-net: FD - SRB (W/m 2 )

52. 52 VI. SRF ALbedo & SW Comparison: FD vs SOB: 15 BEST Stations Selected from BSRN, ARM and SURFRAD networks

53. 53 FD vs SOB: all local noon of 2004 for 15 stations Statistics from all 2004 Local Solar Time = 12 from 3-hour mean ( flux in w/m 2 )

54. 54 Clear-sky SRF albedo FD (X) vs. SOB (Y)

55. 55 Full-sky SRF albedo FD (X) vs. SOB (Y)

56. 56 Clear-sky SRF SW-dw ( W/m 2 ) FD (X) vs. SOB (Y)

57. 57 Full-sky SRF SW-dw ( W/m 2 ) FD (X) vs. SOB (Y)

58. 58 Clear-sky SRF Albedo Diurnal Cycle Comparison: FD vs SOB

59. 59 Clear-sky SRF SW-dw (W/m 2 ) Diurnal Cycle Comparison: FD vs SOB

60. 60 Clear-sky SRF SW-up (W/m 2 ) Diurnal Cycle Comparison: FD vs SOB

61. 61 Full-sky SRF Albedo Diurnal Cycle Comparison: FD vs SOB

62. 62 Full-sky SRF SW-dw (W/m 2 ) Diurnal Cycle Comparison: FD vs SOB

63. 63 Full-sky SRF SW-up (W/m 2 ) Diurnal Cycle Comparison: FD vs SOB

64. 64 Clear-sky SRF Albedo Diurnal Cycle Comparison: FD vs SOB

65. 65 VII. SRF Direct & Diffuse Flux Comparison: FD vs SOB: 15 BEST Stations Selected from BSRN, ARM and SURFRAD networks Statistics from all 2004 Local Solar Time = 12 from 3-hour mean

66. 66 Comparison of Direct/Diffuse Flux Ratio: FD (X) vs SOB (Y): Full Sky

67. 67 SW Difference vs Direct/Diffuse Ratio Difference for FD minus SOB: Full sky

68. 68 Cloud Fraction Comparison: FD cell-mean vs SOB (SW-derived) From 15 BEST Stations Selected from BSRN, ARM and SURFRAD

69. 69 Cloud Fraction vs Direct/Diffuse Ratio: FD cell-mean Located to 15 BEST Stations Selected from BSRN, ARM and SURFRAD

70. 70 Cloud Fraction vs Direct/Diffuse Ratio : SOB (SW derived) From 15 BEST Stations Selected from BSRN, ARM and SURFRAD

71. 71 Comparison of Direct/Diffuse Flux Ratio: FD (X) vs SOB (Y) Clear Sky

72. 72 SW Difference vs Direct/Diffuse Ratio Difference for FD minus SOB: Clear sky

73. 73 Relationship between Column Aerosol Tau & Clear-sky Dir/Diff Ratio from Sensitivity Test on based on NASA GISS Radiative Model

74. 74 After 60% of Column Aerosol Tau Reduction in original FD

75. 75 After 60% of Column Aerosol Tau Reduction in original FD

76. 76 After 60% of Column Aerosol Tau Reduction in original FD

77. 77 After 60% of Column Aerosol Tau Reduction in original FD

78. 78 After 60% of Column Aerosol Tau Reduction in original FD

79. 79 Diurnal Cycle from all 15 Station-mean for July Monthly-hourly mean : Clear-sky Diffuse

80. 80 Diurnal Cycle from all 15 Station-mean for July Monthly-hourly mean : Clear-sky Direct

81. 81 Diurnal Cycle from all 15 Station-mean for July Monthly-hourly mean : Clear-sky Direct to Diffuse Ratio

82. 82 Diurnal Cycle from all 15 Station-mean for July Monthly-hourly mean : Full -sky Diffuse

83. 83 Diurnal Cycle from all 15 Station-mean for July Monthly-hourly mean : Full -sky Direct

84. 84 Diurnal Cycle from all 15 Station-mean for July Monthly-hourly mean : Full -sky Direct to Diffuse Ratio

85. 85 VIII. Uncertainties of Albedo and others and their Caused Global, Daily-mean SW Uncertainties