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Surface Albedo and SW Flux Calculation Y-C. Zhang and W.B.
Rossow
LandFlux ConferenceCNES/CESBIO, Toulouse, FranceMay 28 31,
2007
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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
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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
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Clear-sky Albedo Difference (%): TOA & SRF from FD for
0401
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Clear-sky Albedo Difference (%): TOA & SRF from FD for
0407
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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
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... 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
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... 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
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... 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)
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... 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
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... 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.
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... 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.
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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)
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VIS BSA for four 16-day Period comparison: FD vs. MODIS
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NIR BSA for four 16-day Period comparison: FD vs. MODIS
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Total BSA for four 16-day Period comparison: FD vs. MODIS
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VIS BSA Difference: FD & MODIS for 16-day from 000711
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VIS BSA Difference: FD & MODIS for 16-day from 010117
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NIR BSA Difference: FD & MODIS for 16-day from 000711
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NIR BSA Difference: FD & MODIS for 16-day from 010117
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TTL BSA Difference: FD & MODIS for 16-day from 000711
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TTL BSA Difference: FD & MODIS for 16-day from 010117
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BSA-based Constructed SRF Clr-sky Albedo (%) & SW-up (w/m2):
FD vs. MODIS-FD for July 2000 and January 2001
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SRF Clr-sky Albedo Difference (%): FD & MODIS for July
2000
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SRF Clr-sky Albedo Difference (%): FD & MODIS for Jan.
2001
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TOA Clr-sky Albedo (%): FD vs. MODIS-FD for July 2000 & Jan.
2001:Snow-free Land
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TOA Clr-sky Albedo (%): FD vs. MODIS-FD for July 2000 & Jan.
2001:Snow-covered Land
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TOA Clr-sky SW-up (W/m2): FD vs. MODIS-FDJuly 2000 & Jan.
2001: Snow-free Land
N. Africa & Arabia Peninsula
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TOA Clr-sky SW-up (W/m2): FD vs. MODIS-FDJuly 2000 & Jan.
2001: Snow-covered Land
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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
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.. 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
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Difference of annual-mean TOA Clear-sky Albedo (%): FD - CERES
(Land)
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Difference of annual-mean SRF Clear-sky Albedo (%): FD - CERES
(Land)
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Difference of Annual-mean SRF Clear-sky SW (W/m2): FD - CERES
(Land)
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Difference of Annual-mean SRF Clear-sky SW (W/m2): FD - CERES
(Land)
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Difference of Annual-mean SRF Clear-sky SW-net (W/m2): FD -
CERES (Land)
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Difference of annual-mean TOA Full-sky Albedo (%): FD - CERES
(Land)
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Difference of Annual-mean SRF Full-sky SW (W/m2): FD - CERES
(Land)
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Difference of Annual-mean SRF Full-sky SW (W/m2): FD - CERES
(Land)
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Difference of Annual-mean SRF Full-sky SW-net (W/m2): FD - CERES
(Land)
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Difference of Annual-mean SRF Cloud Effects of Albedo (%): FD -
CERES (Land)
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Difference of Annual-mean SRF Cloud Effects (W/m2): FD - CERES
(Land)
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Difference of January SRF Full-sky Albedo (%): FD - CERES
(Land)
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Difference of January SRF Full-sky SW-net (W/m2): FD - CERES
(Land)
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V. SRF Albedo & SW Comparison: FD vs GEWEX-SRBStatistics for
85-89 Annual-mean Comparison (albedo in % & flux in w/m2)
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85-89 Annual-mean SRF Clear-sky Albedo: FD - SRB (%)
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85-89 Annual-mean SRF Clear-sky SW: FD - SRB (W/m2)
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85-89 Annual-mean SRF Clear-sky SW: FD - SRB (W/m2)
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85-89 Annual-mean SRF SW: FD - SRB (W/m2)
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85-89 Annual-mean SRF SW: FD - SRB (W/m2)
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85-89 Annual-mean SRF SW-net: FD - SRB (W/m2)
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VI. SRF ALbedo & SW Comparison: FD vs SOB:15 BEST Stations
Selected from BSRN, ARM and SURFRAD networks
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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)
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Clear-sky SRF albedo FD (X) vs. SOB (Y)
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Full-sky SRF albedo FD (X) vs. SOB (Y)
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Clear-sky SRF SW-dw (W/m2) FD (X) vs. SOB (Y)
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Full-sky SRF SW-dw (W/m2) FD (X) vs. SOB (Y)
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Clear-sky SRF Albedo Diurnal Cycle Comparison: FD vs SOB
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Clear-sky SRF SW-dw (W/m2) Diurnal Cycle Comparison: FD vs
SOB
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Clear-sky SRF SW-up (W/m2) Diurnal Cycle Comparison: FD vs
SOB
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Full-sky SRF Albedo Diurnal Cycle Comparison: FD vs SOB
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Full-sky SRF SW-dw (W/m2) Diurnal Cycle Comparison: FD vs
SOB
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Full-sky SRF SW-up (W/m2) Diurnal Cycle Comparison: FD vs
SOB
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Clear-sky SRF Albedo Diurnal Cycle Comparison: FD vs SOB
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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
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Comparison of Direct/Diffuse Flux Ratio: FD (X) vs SOB (Y):Full
Sky
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SW Difference vs Direct/Diffuse Ratio Difference for FD minus
SOB: Full sky
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Cloud Fraction Comparison: FD cell-mean vs SOB (SW-derived)From
15 BEST Stations Selected from BSRN, ARM and SURFRAD
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Cloud Fraction vs Direct/Diffuse Ratio: FD cell-meanLocated to
15 BEST Stations Selected from BSRN, ARM and SURFRAD
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Cloud Fraction vs Direct/Diffuse Ratio : SOB (SW derived)From 15
BEST Stations Selected from BSRN, ARM and SURFRAD
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Comparison of Direct/Diffuse Flux Ratio: FD (X) vs SOB (Y)Clear
Sky
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SW Difference vs Direct/Diffuse Ratio Difference for FD minus
SOB: Clear sky
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Relationship between Column Aerosol Tau & Clear-sky Dir/Diff
Ratiofrom Sensitivity Test on based on NASA GISS Radiative
Model
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After 60% of Column Aerosol Tau Reduction in original FD
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After 60% of Column Aerosol Tau Reduction in original FD
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After 60% of Column Aerosol Tau Reduction in original FD
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After 60% of Column Aerosol Tau Reduction in original FD
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After 60% of Column Aerosol Tau Reduction in original FD
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Diurnal Cycle from all 15 Station-mean for July Monthly-hourly
mean :Clear-sky Diffuse
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Diurnal Cycle from all 15 Station-mean for July Monthly-hourly
mean :Clear-sky Direct
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Diurnal Cycle from all 15 Station-mean for July Monthly-hourly
mean :Clear-sky Direct to Diffuse Ratio
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Diurnal Cycle from all 15 Station-mean for July Monthly-hourly
mean :Full-sky Diffuse
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Diurnal Cycle from all 15 Station-mean for July Monthly-hourly
mean :Full-sky Direct
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Diurnal Cycle from all 15 Station-mean for July Monthly-hourly
mean :Full-sky Direct to Diffuse Ratio
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VIII. Uncertainties of Albedo and others and their Caused
Global, Daily-mean SW Uncertainties
Surface albedo causes SW-up has smaller correlation; LW
TsSunglint..