Surface Albedo and SW Flux Calculation Y-C. Zhang and W.B. Rossow

LandFlux ConferenceCNES/CESBIO, Toulouse, FranceMay 28 31, 2007

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-SRBVI. SRF Albedo & SW Comparison: FD vs SOBVII. SRF Direct/Diffuse Fluxes & Their ratio VIII. Uncertainties of Albedo and Others and their Caused Global, Daily-mean SW Uncertainties

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 m ~ SW Visible: ~ 0.2 0.7 m ~ VIS SW Near-Infrared: ~ 0.7 5.0 m ~ 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

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

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

II. Datasets Used1. 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 skySpatial 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

... II. Datasets Used2. MODIS Surface Albedo (and Flux) Product

Version: MOD43C2 V004 L3 (from Crystal Schaaf) Black Sky AlbedoSpatial 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 m (based on 3 channels) NIR 0.7 5.0 m (based on 4 channels)

SW Flux (MODIS-FD) Calculation is based on MODIS BSA using ISCCP-FD production code

... II. Datasets Used3. 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 skySpatial resolution: horizontal: 2.5 X 2.5Temporal 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

... II. Datasets Used4. 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 skySpatial 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 m) from Pinker/Laszlo (quality check by Staylor Model) LW (4.5 m) from Fu/Liou, (quality check by Gupta Model)

... II. Datasets Used5. 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

... II. Datasets Used6. 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 ofTop-of-Atmosphere Reflected Solar Radiation, J. Clim., 20, 575-591.

... 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.

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

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

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

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

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

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

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

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

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

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

BSA-based Constructed SRF Clr-sky Albedo (%) & SW-up (w/m2): FD vs. MODIS-FD for July 2000 and January 2001

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

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

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

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

TOA Clr-sky SW-up (W/m2): FD vs. MODIS-FDJuly 2000 & Jan. 2001: Snow-free Land

N. Africa & Arabia Peninsula

TOA Clr-sky SW-up (W/m2): FD vs. MODIS-FDJuly 2000 & Jan. 2001: Snow-covered Land

IV. SRF Albedo & SW Comparison: FD vs. CERES Averaged from 36-month (0003 to 0302) Global, monthly-mean statistics; SW in W/m2; ALB in %; Cor are without unit

.. SRF Albedo & SW Comparison: FD vs. CERES Averaged from 36-month (0003 to 0302) Land-only, monthly-mean statistics; SW in W/m2; ALB in %; Cor are without unit

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

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

Difference of Annual-mean SRF Clear-sky SW (W/m2): FD - CERES (Land)

Difference of Annual-mean SRF Clear-sky SW (W/m2): FD - CERES (Land)

Difference of Annual-mean SRF Clear-sky SW-net (W/m2): FD - CERES (Land)

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

Difference of Annual-mean SRF Full-sky SW (W/m2): FD - CERES (Land)

Difference of Annual-mean SRF Full-sky SW (W/m2): FD - CERES (Land)

Difference of Annual-mean SRF Full-sky SW-net (W/m2): FD - CERES (Land)

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

Difference of Annual-mean SRF Cloud Effects (W/m2): FD - CERES (Land)

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

Difference of January SRF Full-sky SW-net (W/m2): FD - CERES (Land)

V. SRF Albedo & SW Comparison: FD vs GEWEX-SRBStatistics for 85-89 Annual-mean Comparison (albedo in % & flux in w/m2)

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

85-89 Annual-mean SRF Clear-sky SW: FD - SRB (W/m2)

85-89 Annual-mean SRF Clear-sky SW: FD - SRB (W/m2)

85-89 Annual-mean SRF SW: FD - SRB (W/m2)

85-89 Annual-mean SRF SW: FD - SRB (W/m2)

85-89 Annual-mean SRF SW-net: FD - SRB (W/m2)

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

FD vs SOB: all local noon of 2004 for 15 stationsStatistics from all 2004 Local Solar Time = 12 from 3-hour mean (flux in w/m2)

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

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

Clear-sky SRF SW-dw (W/m2) FD (X) vs. SOB (Y)

Full-sky SRF SW-dw (W/m2) FD (X) vs. SOB (Y)

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

Clear-sky SRF SW-dw (W/m2) Diurnal Cycle Comparison: FD vs SOB

Clear-sky SRF SW-up (W/m2) Diurnal Cycle Comparison: FD vs SOB

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

Full-sky SRF SW-dw (W/m2) Diurnal Cycle Comparison: FD vs SOB

Full-sky SRF SW-up (W/m2) Diurnal Cycle Comparison: FD vs SOB

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

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

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

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

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

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

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

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

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

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

After 60% of Column Aerosol Tau Reduction in original FD

After 60% of Column Aerosol Tau Reduction in original FD

After 60% of Column Aerosol Tau Reduction in original FD

After 60% of Column Aerosol Tau Reduction in original FD

After 60% of Column Aerosol Tau Reduction in original FD

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

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

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

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

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

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

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

Surface albedo causes SW-up has smaller correlation; LW TsSunglint..