improved orbiting carbon observatory-2 (oco-2) retrievals...
TRANSCRIPT
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Page 1 1 of 18 © 2017 California Institute of Technology. Government Sponsorship Acknowledged.
Vijay Natraj (Jet Propulsion Laboratory, California Institute of Technology)
Co-Authors Matthäus Kiel (Caltech)
Aronne Merrelli (University of Wisconsin-Madison/SSEC) James McDuffie (JPL/Caltech) Brendan Fisher (JPL/Caltech)
Chris O’Dell (Colorado State University) David Crisp (JPL/Caltech)
Annmarie Eldering (JPL/Caltech) Dejian Fu (JPL/Caltech)
Debra Wunch (University of Toronto) Paul Wennberg (Caltech)
Lukas Mandrake (JPL/Caltech)
13th International Workshop on Greenhouse Gas Measurements from Space June 6, 2017
Improved Orbiting Carbon Observatory-2 (OCO-2) Retrievals Using a BRDF Model for the
Surface
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Retrieved Albedo Correlated With Scattering Angle
Retrieved albedo correlated with scattering angle => BRDF effects?
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OCO-2 Measurement Geometry
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• w: overall BRDF amplitude [BRDF weight] • s: slope of BRDF amplitude [BRDF weight slope] • λ: wavelength • λ0: reference wavelength (where parameters are retrieved) • F: function describing BRDF shape (RPV kernel) • ρ0: hot spot parameter = 0.05 • θ: asymmetry parameter = −0.1 • k: anisotropy parameter = 0.75 • BRDF kernel reduces to Lambertian kernel for certain choice of BRDF shape
parameters • w, s retrieved
BRDF Formulation
BRDF(λ) = w+ s(λ −λ0 )[ ]F(ρ0,ϑ ,k)
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RPV Kernel Shape
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• w and s converted to more physically meaningful quantities, ρw (reflectance) and ρs (reflectance slope)
• ρw and ρs calculated by evaluating the BRDF kernel model at the primary observation geometry
• Reflectance factor equals ratio between reflected radiance and that from pure Lambertian surface at the same geometry
• For no scattering scenario, this is equivalent to a Lambertian albedo
• Consistency between Lambertian albedo used in B7 and effective albedo used in B8
BRDF Outputs
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Number of Converged Soundings
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Retrieved AOD (Bremen, 9090)
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Retrieved AOD (Caltech, 3052)
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Retrieved XCO2 (Bremen, 9090)
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Retrieved XCO2 (Caltech, 3052)
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Retrieved Albedo (Bremen, 9090)
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Retrieved Albedo (Caltech, 3052)
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Retrieved BRDF Weights (Bremen, 9090)
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Retrieved BRDF Weights (Caltech, 3052)
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• To-do items from last year implemented ü Re-baseline with new spectroscopic models ü How do we compare Lambertian and BRDF results ü Implement BRDF model in operational code
• Increased convergence
• Improved AOD retrievals
• Reduced scatter in XCO2 retrievals
• Consistency in albedo values between B7 and B8
• Strong correlation of albedo with scattering angle
• Little correlation between BRDF weight and scattering angle
Conclusions
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Backup Slides
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OCO-2 Science Viewing Modes
Nadir Observations: + Small footprint (< 3 km2) - Low Signal/Noise over dark
surfaces (ocean, ice)
Glint Observations: + Improves Signal/Noise over
oceans - More cloud interference
Target Observations: • Validation over ground
based FTS sites, field campaigns, other targets
447-
m W
LEF
Tow
er
Park Falls, WI Local Nadir
Glint Spot