AGU Fall Meeting December 4, 2005

Vijay Natraj (California Institute of Technology) Vijay Natraj (California Institute of Technology) Hartmut Bösch (Jet Propulsion Laboratory)Hartmut Bösch (Jet Propulsion Laboratory)

Yuk Yung (California Institute of Technology)Yuk Yung (California Institute of Technology)

Quantifying Aerosol Types and Their Quantifying Aerosol Types and Their Impact on Trace Gas Retrievals From Impact on Trace Gas Retrievals From

Satellite MeasurementsSatellite Measurements

AGU Fall Meeting December 4, 2005

Major Source of Retrieval UncertaintyMajor Source of Retrieval Uncertainty

Ground surface

Aerosol Layer 1

Aerosol Layer 2

Light reaching

the detector

Photon path length is enhanced

through multiple scattering by

aerosols

Incident light

AGU Fall Meeting December 4, 2005

Global Aerosol ClimatologyGlobal Aerosol Climatology

Courtesy: Kahn et al, 2001

AGU Fall Meeting December 4, 2005

Aerosol Optical PropertiesAerosol Optical Properties

• Each mixing group is a combination of 4 different aerosol components from a basic set of 7 (Kahn et al., 2001).

• Sulfate (land/water), seasalt, carbonaceous, black carbon: spherical => Mie code (de Rooij and van der Stap, 1984)

• Mineral dust (accumulated/coarse): mixture of oblate and prolate spheroids => T-matrix code (Mishchenko and Travis, 1998)

• Lognormal distribution

• Polarization fully considered

AGU Fall Meeting December 4, 2005

Scattering Matrix (755 nm)Scattering Matrix (755 nm)

AGU Fall Meeting December 4, 2005

Forward Model DetailsForward Model Details

• Park Falls, Wisconsin, July (SZA = 31 degrees)

• Exponential drop-off in aerosol extinction (scale height: ~ 1 km, optical depth: 0.1)

• OCO spectral regions

• Forward model: RADIANT (Christi, CSU) + single scattering approximation for polarization

• Lorentzian instrument lineshape function (resolving powers: O2 A band: 17000, CO2 bands: 20000)

AGU Fall Meeting December 4, 2005

Weighting Functions (OWeighting Functions (O22 AA Band) Band)

0.758 0.760 0.762 0.764 0.766 0.768 0.770 0.772-10

-8

-6

-4

-2

0

2

4

6

8

No

rma

lize

d J

aco

bia

n

Wavelength [m]

Type 1a 1b 1c 2a 2b 3a 3b 4a 4b 4c 5a 5b 5c

AGU Fall Meeting December 4, 2005

Weighting Functions (Weak COWeighting Functions (Weak CO22 Band) Band)

1.590 1.595 1.600 1.605 1.610 1.615 1.620

-0.4

-0.2

0.0

0.2

0.4 Type 1a 1b 1c 2a 2b 3a 3b 4a 4b 4c 5a 5b 5c

No

rma

lize

d J

aco

bia

n

Wavelength [m]

AGU Fall Meeting December 4, 2005

Weighting Functions (Strong COWeighting Functions (Strong CO22 Band) Band)

2.04 2.05 2.06 2.07 2.08

-0.10

-0.05

0.00

0.05

0.10

No

rma

lize

d J

aco

bia

n

Type 1a 1b 1c 2a 2b 3a 3b 4a 4b 4c 5a 5b 5c

Wavelength [m]

AGU Fall Meeting December 4, 2005

Retrieval Groups: Single Scattering AlbedoRetrieval Groups: Single Scattering Albedo

0.755 0.785 1.56 1.65 2.03 2.090.80

0.85

0.90

0.95

1.00

0.755 0.785 1.56 1.65 2.03 2.090.80

0.85

0.90

0.95

1.00

0.755 0.785 1.56 1.65 2.03 2.090.80

0.85

0.90

0.95

1.00

0.755 0.785 1.56 1.65 2.03 2.090.80

0.85

0.90

0.95

1.00

0.755 0.785 1.56 1.65 2.03 2.090.80

0.85

0.90

0.95

1.00

Type 5b

Wavelength [m]

Sin

gle

Sca

tter

ing

Alb

edo

Group 4Type

3b

Group 5

Type 2b 4b 4c

Sin

gle

Sca

tter

ing

Alb

edo

Group 2

Type 3a 5a 5c

Group 3

Type 1a 1b 1c 2a 4a

Sin

gle

Sca

tter

ing

Alb

edo

Group 1

AGU Fall Meeting December 4, 2005

Retrieval Groups: Normalized Extinction CoefficientRetrieval Groups: Normalized Extinction Coefficient

0.755 0.785 1.56 1.65 2.03 2.090.10.20.30.40.50.60.70.80.91.01.1

0.755 0.785 1.56 1.65 2.03 2.090.10.20.30.40.50.60.70.80.91.01.1

0.755 0.785 1.56 1.65 2.03 2.090.10.20.30.40.50.60.70.80.91.01.1

0.755 0.785 1.56 1.65 2.03 2.090.10.20.30.40.50.60.70.80.91.01.1

0.755 0.785 1.56 1.65 2.03 2.090.10.20.30.40.50.60.70.80.91.01.1

Nor

mal

ized

Ext

inct

ion

Coe

ffici

ent

Type 5b

Wavelength [m]

Group 4

Type 3b

Group 5

Type 2b 4b 4c

Nor

mal

ized

Ext

inct

ion

Coe

ffic

ient Group 2

Type 3a 5a 5c

Group 3

Nor

mal

ized

Ext

inct

ion

Coe

ffici

ent

Type 1a 1b 1c 2a 4a

Group 1

AGU Fall Meeting December 4, 2005

Sensitivity TestsSensitivity Tests

• Measurement error: 0.43 ppm

• Smoothing error: 0.29 ppm

• Error due to incorrect assumption of aerosol type within retrieval group

– Group 1: 0.27 ppm

– Group 2: 0.02 ppm

– Group 3: 0.03 ppm

AGU Fall Meeting December 4, 2005

ConclusionsConclusions

• Aerosol retrieval groups determined from basic aerosol mixing groups

• Choosing incorrect mixing group within retrieval group leads to small errors

• Need to test more scattering geometries to validate retrieval types

• More realistic aerosol profiles need to be included

AGU Fall Meeting December 4, 2005

AcknowledgmentsAcknowledgments

• OCO L2 Team (JPL)

• Matt Christi (CSU)

• Michael Mishchenko (GISS)

• Olga Kalashnikova and Ralph Kahn (JPL)

AGU Fall Meeting December 4, 2005

Related Talks/PostersRelated Talks/Posters

• Charles Miller (A14C-02)

• Hartmut Boesch (A12D-05)

• Gretchen Aleks (A33B-0883)

AGU Fall Meeting December 4, 2005

• Need to consider both atmospheric/surface and instrumental polarization

Importance of PolarizationImportance of Polarization