Ocean Color Reprocessing

Goddard Space

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Ocean Color ReprocessingOcean Color Reprocessing

Bryan Franz

Ocean Biology Processing GroupNASA Goddard Space Flight Center

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Flight CenterContentsContents

• reprocessing overview•known issues•proposed changes•preliminary results• international collaborations

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Flight CenterOverviewOverview

Scope:• sensors: MODISA, MODIST, SeaWiFS, OCTS, CZCS• suites: OC, PAR, CLCT, FLH, POC, ZEU, IOP

Highlights:• sensor calibration updates (instrument aging, new insights)• vicarious calibration updates (new MOBY data)• new aerosol models based on AERONET • NO2 corrections• change MODIS nominal band center• traceability & reproducibility of all inputs

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Flight CenterWe're not doing bad "as is"We're not doing bad "as is"

"first, do no harm" --Hippocrates

SeaWiFS MODISA

APDRatioNSubset

37%1.182004All

29%0.99466Deep

APDRatioNSubset

39%1.15589All

21%0.9189Deep

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Flight CenterKnown IssuesKnown Issues

0.01 - 0.02 mg m-3

MODIS and SeaWiFS Oligotrophic Chlorophyll

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551 vs 555

667 vs 670

MODIS and SeaWiFS Deep-Water Lwn Ratios

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FLH

Mean FLH = 0.005

MODIS Fluorescence Line Height Global Deep-Water Anomaly Trend

Mission Time

2004 20072007 2006

20%

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ChangesChanges

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Flight CenterAerosol ModelsAerosol Models

• based on AERONET size distributions & albedos• 70 models (7 humidities x 10 size fractions)• model selection descriminated by relative humidity• vector RT code accounting for polarization• same code used for Rayleigh LUTs

c50

c90

Current S&F Size Distributions AeroNET Size Distributions

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Flight CenterRevised Out-of-Band CorrectionsRevised Out-of-Band Corrections

551 547

Revised Band Center

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Flight Center

Year Time

1998 12:04

1999 12:02

2000 12:00

2001 12:01

2002 12:03

2003 12:08

2004 12:15

2005 12:25

2006 12:36

2007 12:50

2008 13:09

2009 13:32

2010 14:02

2011 14:38

2012 15:22

Nod

e C

ross

ing

Tim

e

SeaWiFS OrbitSeaWiFS Orbit

• orbit has drifted to a 1:30 p.m. node crossing

• impact to: attitude system (Sun sensors) solar diffuser calibration thermal environment solar path geometry

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Flight CenterSeaWiFS OrbitSeaWiFS Orbit

Year Time

1998 12:04

1999 12:02

2000 12:00

2001 12:01

2002 12:03

2003 12:08

2004 12:15

2005 12:25

2006 12:36

2007 12:50

2008 13:09

2009 13:32

2010 14:02

2011 14:38

2012 15:22

Nod

e C

ross

ing

Tim

e

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Flight CenterSeaWiFS Temporal Calibration - CurrentSeaWiFS Temporal Calibration - Current

Operational Model

Lunar Observations

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Flight CenterSeaWiFS Temporal Calibration - RevisedSeaWiFS Temporal Calibration - Revised

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Flight CenterSeaWiFS Temporal Calibration IssueSeaWiFS Temporal Calibration Issue

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Flight CenterUncertainty in SeaWiFS nLw TrendsUncertainty in SeaWiFS nLw Trends

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Flight CenterUncertainty in SeaWiFS Chl TrendsUncertainty in SeaWiFS Chl Trends

OC3

OC4

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Oligotrophic Eutrophic

OC3

OC4

Mesotrophic

variation in retrieved chl trend due to uncertainty in lunar-view to earth-view gain ratio at 765nm.

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Flight CenterOther ChangesOther Changes

• MODISA calibrations unknown temporal trend in Red-NIR RVS recharacterize polarization sensitivity, 412 drift

• NO2 corrections Ahmad et al. (2007) Appl. Opt. extensive effort to produce/qc filled gome-schiamachy-omi dataset 0-10 % effects on Lwn, mostly coastal and high latitude

• Updates to ancillary fields best available ozone and met data, new dependency on RH

• Reduction of SeaWiFS "straylight" speckling issues outlier-resistant Level-3 binning strategies

• Updated OCx chlorophyll & Kd algorithms based on NOMAD V2

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ResultsResults

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Flight CenterSeaWiFS Deep-Water In situ Match-up Stats

Product Med Ratio APD N Slope Intercept R-Squared

Lwn412 1.0149 12.4190 171 1.0526 -0.0259 0.8801 Lwn443 0.9453 16.1420 252 1.0219 -0.0908 0.8112 Lwn490 0.9222 13.2710 251 0.9125 0.0167 0.7196 Lwn510 0.9548 13.8035 142 0.9172 0.0302 0.4385 Lwn555 0.9590 16.4210 252 0.7742 0.0653 0.6453 Lwn670 1.6866 79.9820 248 1.2104 0.0121 0.4412

chlorophyll 0.9995 29.8490 466 0.8834 -0.1714 0.7892 aot865 1.4177 42.3055 60 1.4115

Product Med Ratio APD N Slope Intercept R-Squared

Lwn412 1.0013 11.7425 160 1.0148 -0.0181 0.8886 Lwn443 0.9418 16.3365 238 1.0393 -0.1221 0.8198 Lwn490 0.9119 14.5100 237 0.9390 -0.0279 0.7206 Lwn510 0.9767 13.4330 133 0.9508 0.0005 0.4568 Lwn555 0.9450 18.0115 238 0.7707 0.0637 0.6413 Lwn670 1.5503 75.4955 234 1.2204 0.0113 0.4547

chlorophyll 0.9944 26.4870 423 0.8749 -0.2078 0.7931 aot865 1.0631 25.1590 57 1.0583 -0.0028 0.7360

Operational Processing Configuration

Current Baseline Reprocessing Configuration

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Flight CenterImproved Aerosol RetrievalsImproved Aerosol Retrievals

Improved AOT and Angstrom Comparisons

Chlorophyll Unchanged

SeaWiFS Lower Cheseapeake Bay Time-SeriesSeaWiFS Lower Cheseapeake Bay Time-Series

after

before

after

before

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after

before

after

before

Chlorophyll Unchanged

Even Better Using Regional Aerosol Models

SeaWiFS Lower Cheseapeake Bay Time-SeriesSeaWiFS Lower Cheseapeake Bay Time-Series

Improved Aerosol RetrievalsImproved Aerosol Retrievals

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Flight CenterImproved Agreement Between SensorsImproved Agreement Between Sensors

more work TBD on MODISA calibration

Mean Deep-Water Lw Ratio Trends

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Flight CenterSeaWiFS Red-Band IssueSeaWiFS Red-Band Issue

MODISA

SeaWiFS

Eutrophic

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Before After

Mission Time Mission Time

Improved Agreement Between Sensors

Mean Oligotrophic Chlorophyll Trends

Mean Diff = 0.006 mg m-3Mean Diff = 0.013 mg m-3

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Flight CenterOther MissionsOther Missions

• MODIST see Franz et al. (2008) J. Appl. Rem. Sens. see Kwiatkowska et al. (2008) Appl. Opt. make changes consistent with MODISA regenerate vicarious instrument characterization

• CZCS update vicarious calibration (model-based) reprocess with latest tables, algorithms, flags & masks

• OCTS update vicarious calibration (model-based) reprocess with latest tables, algorithms, flags & masks

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Flight CenterSummarySummary

• it’s a big job! SeaWiFS (11+ years), MODISA (6+ years), MODIST (9+ years) instruments aging, orbits changing

• first complete end-to-end re-evaluation and update of ocean color processing methodology, radiative transfer tables, sensor cal, ancillary sources, file formats, etc.

• good progress and demonstrated improvements to date.

• more details and full analyses will be posted online for community comment and feedback.

• start reprocessing of SeaWiFS and MODISA within few months, then MODIST, SST, legacy missions, PAR, IOPs, etc.

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International CollaborationsInternational Collaborationskeeping the time-series alivekeeping the time-series alive

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Flight CenterESA-NASA Collaborations on MERISESA-NASA Collaborations on MERIS

• G. Meister & B. Franz members of MERIS Quality Working Group• providing review and analysis for MERIS reprocessing

• sharing ideas and gaining insight

• CoastColor• OBPG applied to be a "champion user" for MERIS full resolution data

• access to archive of 300-meter Chesapeake Bay scenes

• awaiting ESA decision

• SeaDAS• MERIS display support added

• MERIS processing capability developed

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Flight CenterMERIS Processed with NASA AlgorithmsMERIS Processed with NASA Algorithms

OC4 ChlorophyllRGB

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Flight CenterISRO-NASA Collaborations on OCMISRO-NASA Collaborations on OCM

•OCM-2 is global 1-km, 8-band tilting CCD with lunar calibration

•Implementing arrangements in development for OCM-2 ISRO-NASA & ISRO-NOAA

•ISRO to provide online access to global OCM-2 data (4km) at Level-1B for research use, to all international users, at no cost.

•NASA to provide processing capability (Level-1B through Level-3) for use by ISRO and the international community (SeaDAS). preliminary capability based on OCM-1 already implemented need ISRO to finalize Level-1B format

•NASA & NOAA to participate in Joint Cal/Val Team

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Thank YouThank You

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Rvf Rvc

σf

σc

Cvf

Cvc

Rvf : Geometric mean radius (fine mode)

σf : Geometric standard dev. (fine mode)

Cvf: Max value of the fine mode dist.

Rcf : Geometric mean radius (coarse mode)

σc : Geometric standard dev. (coarse mode)

Ccf: Max value of the coarse mode dist.

fvf = Cvf/(Cvf+Cvc): Fraction of fine mode

fvc = 1-fvf : Fraction of coarse mode

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<0.762>

<0.096>

<0.425>

<0.666>

<0.267>

SERC

Wallop Island

COVE

Modal Radius Standard Deviation

Effective Radius Fine Mode Fraction

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Fine Mode Coarse Mode

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Flight CenterSpectral Out-of-Band CorrectionsSpectral Out-of-Band Corrections

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Flight CenterSeaWiFS Temporal CalibrationSeaWiFS Temporal Calibration

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Flight CenterComparison with Morel (CComparison with Morel (Caa=0.065)=0.065)

MODISA:

Theoretical nLw(547) = 0.319248

Observed nLw(547) = 0.320000


Observed nLw(667) = 0.0230000

SeaWiFS:


Observed nLw(555) = 0.305000


Observed nLw(670) = 0.0400000

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Oligotrophic

Eutrophic

Comparison Ratio

OC3

OC4

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Flight CenterEffect of a Known UnknownEffect of a Known Unknown

Gain 3 Option 1 Gain 3 Option 2 Gain 3 Option 3

Lwn(555) Lwn(555) Lwn(555)

Chl Chl Chl

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Flight CenterUncertainty in SeaWiFS Lwn TrendsUncertainty in SeaWiFS Lwn Trends

Oligotrophic Eutrophic

Mesotrophicvariation in retrieved nLw trend due to uncertainty in lunar-view to earth-view gain ratio at 765nm.

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Flight CenterKnown Issues: SeaWiFS Late-Mission Known Issues: SeaWiFS Late-Mission

SeaWiFS Lw(510) Anomaly

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Flight CenterRemoved Late-Mission Drift in SeaWiFS Removed Late-Mission Drift in SeaWiFS

Before

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Flight CenterKnown Issues: MODISA Lw(412) Trend Known Issues: MODISA Lw(412) Trend

Documents

Ocean Color Reprocessing