norman g. loeb · compared to erbe adms. - large bias in terra sw toa flux for arctic sea-ice....
TRANSCRIPT
Norman G. LoebHampton University/NASA Langley Research Center
Hampton, VA
Contributors: S. Kato, K. Loukachine, N. M. Smith, Q. Trepte
November 1st, 2005, CERES STM (Hampton, VA)
CERES Aqua Angular Distribution Models
Aqua ADM Development
- Developed using Aqua Edition1B SSFs from August 2002 – June 2004 (23 months).
- Same approach as was used to develop and apply Terra ADMs.=> Main difference between Terra and Aqua approach is
in scene identification (clouds).
Uncertainty in Regional Mean SW TOA Flux
APPROACH
i) Construct 10°x10° latitude-longitude regional ADMs by season (e.g., DJF, JJA) from:
i) Measured CERES radiancesii) Radiance predicted by CERES ADMs
ii) Apply regional ADMs to determine fluxes from the same data using one month of crosstrack measurements.
iii) Determine regional mean error in SW TOA flux.
Note: This approach considers only footprints with non-default cloud properties.
DJF MAM
JJA SON
SW TOA Flux Error (W m-2)
Regional Mean SW TOA Flux Errors due to ADM Uncertainties (Terra)
DJF MAM
JJA SON
SW TOA Flux Error (W m-2)
Regional Mean SW TOA Flux Errors due to ADM Uncertainties (Aqua)
- Aqua tests use 2.1 μm channel, Terra tests use 1.6 μm.
- In Aqua Ed1, thresholds of snow and cloud detection were changed in most of branches:-> the clear land and open ocean detection uses T11
instead of Tskin.
- The mini-mask for classifying TBD pixels changed. More of these are being retrieved on Aqua.
- Added Twilight MODIS Polar Tests in Aqua Ed1 that separates super cold plateau and non-super cold polar regions.
- Thin Ci tests remained the same. For daytime polar, the thin Ci tests (based on T11-T12) were in Terra Ed2 already.
Differences between Terra Ed2 and Aqua Ed1 Daytime Polar Cloud Mask
Terra SSF_Ed2B minus Terra SSF_Ed2_Test(July 1, 2003)
Terra SSF_Ed2B: Uses Terra sea-ice ADMsTerra SSF_Ed2_Test: Uses Aqua sea-ice ADMs
Fraction of CERES Fluxes Estimated using Neural Network ADMs
Aqua, July 2003, FAPS
Terra, July 2003, FAPS
Aqua: fewer “cloud no retrievals” than Terra overArctic sea-ice, but more elsewhere.
Terra: significant fraction of “cloud no retrievals” over Arctic sea-ice.
TOA SW Radiative Effect of “Cloud No Retrievals” Footprints(No Diurnal Averaging)
F(all) – F(ADM), Terra, July 2003, FAPS
Terra: “cloud no retrievals” footprintsincrease SW TOA flux over Arctic sea-ice.⇒ Strong dependence upon Neural Network ADMs
F(all) – F(ADM), Aqua, July 2003, FAPSAqua: Weak dependence up NeuralNetwork ADMs.
Uncertainty in Regional Mean LW TOA Flux
SW TOA Flux Error (W m-2)
DJF MAM
JJA SON
Regional Mean LW TOA Flux Errors due to ADM Uncertainties (Terra)
LW TOA Flux Error (W m-2)
DJF MAM
JJA SON
Regional Mean LW TOA Flux Errors due to ADM Uncertainties (Aqua)
Regional Mean Nighttime LW TOA Flux Errors due to ADMs (Aqua)DJF
LW TOA Flux Error (W m-2)
JJA SON
MAM
Nighttime LW TOA Flux Error Against Viewing Zenith Angle (5° x 5° latitude-longitude regions; SON, 2003)
AQUA TERRA
TOA
Flu
x E
rror
(W m
-2)
(-77.5°, -102.5°)(-77.5°, 22.5°)(-77.5°, 102.5°)
Nighttime Polar Cloud Mask Changes between Terra Ed2 and Aqua Ed1
- In Aqua Ed1, over the super Cold Plateau regions, the snow/ice tests were changed so as to slightly reduce cloud cover compared to Terra Ed2.
-> In Terra Ed2, Antarctic ice caps were sometimes misidentified as clouds.
Note: super cold ice cap definition: Tskin < 230 K, T11 < 230 K, elevation > 1000 m and IceMap > 0
Cloud mask changes:Clouds: Tskin > 230 and T11 < 240 and Tcs - T11 > 15 and T3.7-T12 > 4 (Aqua)
Tskin > 230 and T11 < 240 and Tcs - T11 > 12 and T3.7-T12 > 4 (Terra)
Ice: T11 < 220 and T67 - T 11 > 5 and T11 - T12 < 0.7 (Aqua)
T11 < 210 and T67 - T 11 > 9 and T11 - T12 < 0.7 (Terra)
Nighttime Clear Area Coverage and Surface Skin Temperature over Permanent Snow (October 2003)
Clear Area Coverage Surface Skin Temperature (Clear)
Viewing Zenith Angle (°)
Terra and Aqua LW Nighttime ADMs for Permanent Snow
Instantaneous TOA Flux Uncertainty
Instantaneous TOA Flux Consistency Tests
ImagerCERES
1°
1°
θ
(
- Convert imager nadir visible radiance to broadband flux- Compare off-nadir CERES flux with nadir flux inferred from
imager visible radiance.
Consistency = [F(θ=50°-60°) - F (Nadir)] / F (Nadir)] x 100%
Aqua: 47 Days, N FOV = 401,239Terra: 48 days, N FOV = 545,018Aqua: 47 Days, N FOV = 401,239Terra: 48 days, N FOV = 545,018
SSF Cloud Classification(Each Cloud Layer)
SSF Cloud Classification(Each Cloud Layer)
Thick
6
15
24
Mod
5
14
23
Thin
4
13
22
MCL
ThickModThinThickModThin
987321Low
181716121110Mid
272625212019High
OVCPCL
Thick
6
15
24
Mod
5
14
23
Thin
4
13
22
MCL
ThickModThinThickModThin
987321Low
181716121110Mid
272625212019High
OVCPCL
Low: EP > 680 mb
Mid: EP = 440 – 680 mb
High: EP < 440 mb
Thick: t > 22.63OVC: CF = 99 – 100%Mod: τ = 3.35 – 22.63MCL: CF = 40 – 99%
Thin: τ < 3.35PCL: CF = 0.1 - 40%
Low: EP > 680 mb
Mid: EP = 440 – 680 mb
High: EP < 440 mb
Thick: t > 22.63OVC: CF = 99 – 100%Mod: τ = 3.35 – 22.63MCL: CF = 40 – 99%
Thin: τ < 3.35PCL: CF = 0.1 - 40%
No-Glint Ocean Scene TypeSW TOA Flux RMS (%)
No-Glint Ocean Scene TypeSW TOA Flux RMS (%)
6.27
CLR
ThickMod
5.28
10.73
Thin
7.31
MCL
ThickModThinThickModThin
3.563.0628.519.687.77Low
4.155.65Mid
3.726.8411.64High
OVCPCL
6.27
CLR
ThickMod
5.28
10.73
Thin
7.31
MCL
ThickModThinThickModThin
3.563.0628.519.687.77Low
4.155.65Mid
3.726.8411.64High
OVCPCL
Terra Ocean: All-sky RMS = 4.07% (5.21%)Terra Ocean: All-sky RMS = 4.07% (5.21%)
Aqua Ocean: All-sky RMS = 4.23% (6.04%) Aqua Ocean: All-sky RMS = 4.23% (6.04%)
5.28
CLR
ThickMod
6.13
Thin
10.63
MCL
ThickModThinThickModThin
3.613.7825.5010.068.33Low
4.205.6216.01Mid
3.996.7010.21High
OVCPCL
5.28
CLR
ThickMod
6.13
Thin
10.63
MCL
ThickModThinThickModThin
3.613.7825.5010.068.33Low
4.205.6216.01Mid
3.996.7010.21High
OVCPCL
Land SW TOA Flux RMS (%)
Land SW TOA Flux RMS (%)
4.12
CLR
ThickMod
5.97
7.36
Thin
16.53
MCL
ThickModThinThickModThin
4.366.438.108.65Low
4.115.0416.385.30Mid
3.926.0123.274.09High
OVCPCL
4.12
CLR
ThickMod
5.97
7.36
Thin
16.53
MCL
ThickModThinThickModThin
4.366.438.108.65Low
4.115.0416.385.30Mid
3.926.0123.274.09High
OVCPCL
Terra Land: All-sky RMS = 5.77% (4.90%)Terra Land: All-sky RMS = 5.77% (4.90%)
Aqua Land: All-sky RMS = 6.58% (5.03%) Aqua Land: All-sky RMS = 6.58% (5.03%)
3.05
CLR
ThickMod
10.81
7.85
Thin
MCL
ThickModThinThickModThin
4.434.837.6510.59Low
3.064.774.63Mid
4.658.119.793.01High
OVCPCL
3.05
CLR
ThickMod
10.81
7.85
Thin
MCL
ThickModThinThickModThin
4.434.837.6510.59Low
3.064.774.63Mid
4.658.119.793.01High
OVCPCL
Snow/Ice SW TOA Flux RMS (%)
Snow/Ice SW TOA Flux RMS (%)
7.22
CLR
ThickMod
10.77
9.54
Thin
9.04
7.08
11.26
MCL
ThickModThinThickModThin
6.475.988.5017.0110.05Low
15.274.8710.2812.426.21Mid
9.406.199.97High
OVCPCL
7.22
CLR
ThickMod
10.77
9.54
Thin
9.04
7.08
11.26
MCL
ThickModThinThickModThin
6.475.988.5017.0110.05Low
15.274.8710.2812.426.21Mid
9.406.199.97High
OVCPCL
Terra Snow/Ice: All-sky RMS = 8.50% (8.17%) Terra Snow/Ice: All-sky RMS = 8.50% (8.17%)
Aqua Snow/Ice: All-sky RMS = 8.23% (7.40%)Aqua Snow/Ice: All-sky RMS = 8.23% (7.40%)
5.02
CLR
ThickMod
14.18
10.16
Thin
11.54
6.19
MCL
ThickModThinThickModThin
5.178.8517.509.79Low
6.977.3510.125.37Mid
8.798.656.04High
OVCPCL
5.02
CLR
ThickMod
14.18
10.16
Thin
11.54
6.19
MCL
ThickModThinThickModThin
5.178.8517.509.79Low
6.977.3510.125.37Mid
8.798.656.04High
OVCPCL
SW TOA Flux Consistency by Cloud Fraction and Cloud Height
(Ocean)
Ocean LW TOA Flux RMS (%)
Ocean LW TOA Flux RMS (%)
0.97
CLR
ThickMod
2.42
5.13
Thin
1.06
MCL
ThickModThinThickModThin
2.422.242.511.080.96Low
4.844.47Mid
7.317.796.351.95High
OVCPCL
0.97
CLR
ThickMod
2.42
5.13
Thin
1.06
MCL
ThickModThinThickModThin
2.422.242.511.080.96Low
4.844.47Mid
7.317.796.351.95High
OVCPCL
Aqua Ocean: All-sky RMS = 2.39% (2.30%)Aqua Ocean: All-sky RMS = 2.39% (2.30%)
1.06
CLR
ThickMod
0.99
Thin
1.05
MCL
ThickModThinThickModThin
1.961.520.710.73Low
2.284.721.02Mid
5.977.696.041.05High
OVCPCL
1.06
CLR
ThickMod
0.99
Thin
1.05
MCL
ThickModThinThickModThin
1.961.520.710.73Low
2.284.721.02Mid
5.977.696.041.05High
OVCPCL
Terra Ocean: All-sky RMS = 2.66% (2.63%)Terra Ocean: All-sky RMS = 2.66% (2.63%)
Land LW TOA Flux RMS (%)
Land LW TOA Flux RMS (%)
1.85
CLR
ThickMod
1.43
3.69
Thin
3.26
MCL
ThickModThinThickModThin
2.251.271.962.00Low
2.073.941.882.00Mid
7.588.515.622.65High
OVCPCL
1.85
CLR
ThickMod
1.43
3.69
Thin
3.26
MCL
ThickModThinThickModThin
2.251.271.962.00Low
2.073.941.882.00Mid
7.588.515.622.65High
OVCPCL
Aqua Land: All-sky RMS = 2.94% (1.97%)Aqua Land: All-sky RMS = 2.94% (1.97%)
1.60
CLR
ThickMod
1.18
3.42
Thin
MCL
ThickModThinThickModThin
1.641.351.531.57Low
3.353.772.15Mid
5.906.752.412.42High
OVCPCL
1.60
CLR
ThickMod
1.18
3.42
Thin
MCL
ThickModThinThickModThin
1.641.351.531.57Low
3.353.772.15Mid
5.906.752.412.42High
OVCPCL
Terra Land: All-sky RMS = 3.41% (2.09%)Terra Land: All-sky RMS = 3.41% (2.09%)
Snow/Ice LW TOA Flux RMS (%)
Snow/Ice LW TOA Flux RMS (%)
2.85
CLR
ThickMod
2.22
2.23
Thin
2.45
2.36
2.3 9
MCL
ThickModThinThickModThin
5.542.195.482.342.12Low
3.844.854.005.592.35Mid
4.105.165.152.58High
OVCPCL
2.85
CLR
ThickMod
2.22
2.23
Thin
2.45
2.36
2.3 9
MCL
ThickModThinThickModThin
5.542.195.482.342.12Low
3.844.854.005.592.35Mid
4.105.165.152.58High
OVCPCL
Aqua Snow/Ice: All-sky RMS = 2.13% (2.26%)Aqua Snow/Ice: All-sky RMS = 2.13% (2.26%)
2.27
CLR
ThickMod
1.61
2.50
Thin
1.96
2.05
MCL
ThickModThinThickModThin
1.612.431.372.19Low
3.401.841.522.96Mid
7.465.012.20High
OVCPCL
2.27
CLR
ThickMod
1.61
2.50
Thin
1.96
2.05
MCL
ThickModThinThickModThin
1.612.431.372.19Low
3.401.841.522.96Mid
7.465.012.20High
OVCPCL
Terra Snow/Ice: All-sky RMS = 2.78% (2.87%)Terra Snow/Ice: All-sky RMS = 2.78% (2.87%)
- CERES TOA flux uncertainties from new CERES ADMs: => 1σ regional mean TOA flux : < 1 W m-2
=> Instantaneous SW TOA flux : 10 -15 W m-2
=> Instantaneous LW TOA flux : 5 -10 W m-2
- Significant reduction in albedo dependence on viewing zenith angle compared to ERBE ADMs.
- Large bias in Terra SW TOA flux for Arctic sea-ice. Important changes in cloud mask lead to improvements for Aqua.=> Suggest using Aqua sea-ice ADMs in Terra Ed3 processing.
- Large bias in Aqua nighttime LW fluxes over permanent snow. Important changes in cloud mask resulted in large biases for Aqua.=> Suggest using Terra nighttime LW permanent snow ADMs in Aqua
Ed2A processing.
- Evidence for a dependence in clear ocean instantaneous uncertainty on aerosol fine-mode fraction.=> Suggest incorporating fine-mode fraction for Terra and Aqua Ed3
processing.
Summary