# Presentation: 202737

## Ocean Color Reprocessing

- Bryan Franz
- and the
- Ocean Biology Processing Group

*MODIS/VIIRS Science Team Meeting, 14 May 2008, Baltimore, MD*

## Contents

- Current Processing Status
- Changes Planned for Reprocessing
- Summary

## The Great Ocean Color Reprocessing 

- Scope:
- sensors: MODISA, MODIST, SeaWiFS, OCTS, CZCS
- suites: **OC**, PAR, CLCT, FLH, POC, ZEU, IOP
*software & analysis by Sep, processing by end of 2008*
- Goals:
- improve absolute accuracy of derived products (L2 & L3)
- reduce instrumental artifacts (temporal & spatial)
- improve agreement between sensors
- update product format & content, filenames, flags/masks
- comprehensive product and software documentation

## Previous (Re)processings

| Sensor | Date | Version |
| --- | --- | --- |
| SeaWiFS | Jul 2005 | 5.1 |
| MODIS-Aqua | Aug 2005 | 1.1 |
| OCTS | Oct 2006 | 1.0 |
| CZCS | Oct 2006 | 1.0 (+nav update) |
| MODIS-Terra | Jan 2007 | 0.0 (forward only) |

- Since 2007: focusing on MODIS-Terra characterization, coastal processing, new products, new missions, publication

## Slide 5

## Previous (Re)processings

**SeaWiFS R5.2**
-  updated instrument calibration
-  updated vicarious cal, latest MOBY dataset, filtering

| Sensor | Date | Version |
| --- | --- | --- |
| SeaWiFS | Jul 2005 | 5.1 |
| MODIS-Aqua | Aug 2005 | 1.1 |
| OCTS | Oct 2006 | 1.0 |
| CZCS | Oct 2006 | 1.0 (+nav update) |
| MODIS-Terra | Jan 2007 | 0.0 (forward only) |
| SeaWiFS | Jul 2007 | 5.2 |

## Chlorophyll DifferencesMODIS/Aqua - SeaWiFS

**Oligotrophic**

- 0.01 - 0.02 mg m-3

## SeaWiFS instrument calibration
time & temperature, revised pre-launch cal 

MODISA instrument calibration
OBC LUT update, RVS shape, red bands

MODIST instrument calibration
vicarious characterization

OCTS, CZCS instrument calibration
no updates

Vicarious cal
update MOBY Lw from source, new filtering technique

- time & temperature, revised pre-launch cal
- MODISA instrument calibration
- OBC LUT update, RVS shape, red bands
- MODIST instrument calibration
- vicarious characterization
- OCTS, CZCS instrument calibration
- no updates
- Vicarious cal
- update MOBY Lw from source, new filtering technique

- Planned Calibration Updates

## Updated nLw Bandpass Corrections

## SeaWiFS Relative Spectral Response

## SeaWiFS nLw Bandpass Corrections

## Aqua nLw Bandpass Corrections

## Measured vs Specified Band Centers

## Rederive OC chlorophyll algorithms 

- OC3: CZCS, MODISA, MODIST,  OC4: SeaWiFS, OCTS
- empirical max band ratio algorithms fit to NOMAD v2

## based on AERONET size distributions, SSA
accounting for polarization in the RT
revised band centers
need to assess impact to global products
see poster by Z. Ahmad

- accounting for polarization in the RT
- revised band centers
- need to assess impact to global products
- see poster by Z. Ahmad

- New Aerosol Model Suite

- c50

- c90

## SeaWiFS Speckling

- Lwn(555)

- bbp(443)

## flags & masks
add bad-value meta-data to L2 products, mask in L3
allow negative radiances in binner 

can we improve on nLw(NIR) model?
lessons learned from SSR modeling
also applies to CZCS red nLw

f/Q corrections
yes or no
table updates?

Gordon BRDF correction for diffuse transmittance
yes or no

- add bad-value meta-data to L2 products, mask in L3
- allow negative radiances in binner
- can we improve on nLw(NIR) model?
- lessons learned from SSR modeling
- also applies to CZCS red nLw
- f/Q corrections
- yes or no
- table updates?
- Gordon BRDF correction for diffuse transmittance
- yes or no

- Other Considerations

## CZCS
update vicarious calibration (model-based)
update Lw(670) model (revised Lw(NIR) model)
reprocess with latest tables, algorithms, flags & masks

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

- update vicarious calibration (model-based)
- update Lw(670) model (revised Lw(NIR) model)
- reprocess with latest tables, algorithms, flags & masks
- OCTS
- update vicarious calibration (model-based)
- reprocess with latest tables, algorithms, flags & masks

- Legacy Missions

## Summary

- Instrument calibration & characterization updates
- SeaWiFS speckling
- Bandpass corrections and revised band centers
- Chlorophyll algorithms updated to NOMAD-v2
- Aerosol models updated to match AERONET

## Thank you

## Slide 21

## Seasonal Anomaly TrendsnLw(55x) in Oligotrophic Waters

**SeaWiFS**

## Lt() - [M11LI() + M12LQ() + M13LU()]

- MODIS – vicarious TOA radiance (unpolarized)

- gas

-  glint

-  whitecap

-  air

-  aerosol

- LI() = [ Lr() + La() + tLf() + TLg() + td()Lw() ] · tg()

- water

- Lt() - [M11LI() + M12LQ() + M13LU()]

- minimize over global distribution of path geometries to find
- best M11, M12, M13 per band, detector, and mirror-side
- do this for one day per month over the mission lifespan

## MODIS-Terra Residual RVS in nLw

- 412

- 443

- After Vicarious Characterization

- 488

- 412

- 443

- 488

- Before Vicarious Characterization

## MODIS-Terra and MODIS-Aqua nLw

- After Vicarious Characterization

- Before Vicarious Characterization