# Presentation: 209197

## MODIS Ocean Color Processing

**MODIS Ocean Color Processing**

**Chuck McClain***
**Processing Approach Calibration/Validation**
**Gene Feldman***
**Data Processing & Distribution**
- MODIS Team Meeting/ July 13-15, 2004/Baltimore, MD
-                                                                      * NASA/GSFC

**Notes:**
 monitoring harmful blooms from space gives coastal communities ability to take precautionary measures
 fishing bans
 beach closures
 image shows true color (top) and chlorophyll (bottom)  views of bloom in mouth of Mississippi
 similar information was used to monitor a red tide bloom off coast of Texas last fall

## MODIS Ocean Processing Reorganization

- MODIS Ocean Color processing reorganized by NASA HQ to coincide with new MODIS Ocean Science Team selection.
- Ocean color to lead the NASA Earth Science Enterprise transition to “discipline processing”, i.e., move from “missions to measurements” processing.
- Operational ocean color data processing transferred from MODAPS to the Ocean Color Discipline Processing Group on February 1.
- SST processing remains at MODAPS until HQ defines an alternative processing structure.

## Ocean Color Discipline Processing System

_**MAIN PROCESSING SYSTEM**_
*Data from multiple satellite and instrument types*
*In-situ, ancillary, and other data*

- GSFC
- DAAC

**Flexible**
**Processing**
** *****Multiple Missions***
*** ******Rapid Reprocessing***
*** ******Parallel Processing***
***Streams (operational,***
***algorithm & cali-***
***ration testing, eval-***
***uation products)***

**Science**
**Community**
**Interactive**
*** ******Knowledgable Staff***
*** ******Enabling Activities***
***(SeaBASS, SeaDAS,***
***Calibration RR, etc.)***

***                             ******OCDP  Management & Staff***

***Reconfigurable & Scalable***

**Science**
**Community**

**NASA **
**Flight Projects**

**NASA HQ**
**Program **
**Management**

**Ocean Color Discipline Processing System**

***Community Agreed ***
***Standards and Protocols***

**In Situ Data**

- Data
- Users

**L1 ****DATA**

**L1-L3 DATA**

**MCST***

*** MODIS Characterization Support Team (NASA/GSFC)**

## MODIS OC Processing Strategy

**Initial focus on MODIS/Aqua**
- MODIS/Aqua more stable than MODIS/Terra
- MODIS/Aqua overlap with NPP/VIIRS
**Initial emphasis on calibration & Lwn’s**
- Large seasonal/regional differences between MODIS/(Terra & Aqua) & SeaWiFS Lwn’s
**Reduced product set until radiometry verified**
- Simplify processing for radiometry evaluations
- Maintain a baseline consistent with SeaWiFS product suite.  Expand product suite later.

## MODIS Ocean Color Parameters

**Previous OC Parameter Set**
- Normalized water-leaving radiances (7)
- Aerosol optical thickness (865 nm)
- Atmospheric correction epsilon
- Aerosol model numbers (2)
- Clear water aerosol correction epsilon
- CZCS pigment concentration
- Chlorophyll-a concentration (3)
- Total pigment concentration
- Chlorophyll fluorescence line height
- Chlorophyll fluorescence baseline
- Chlorophyll fluorescence efficiency
- Total suspended matter
- Coccolithophore pigment concentration
- Detached coccolithophore concentration
- Calcite concentration
- Diffuse attenuation at 490 nm
- Phycoerythobilin concentration
- Phycourobilin concentration
- Instantaneous PAR
- Instantaneous absorbed radiation for fluorescence
- Gelbstoff absorption coefficient at 400 nm
- Phytoplankton absorption coefficient at 675 nm
- Total absorption coefficients (5)
- Primary production (2 at Level-4)

**Current OC “Baseline” Parameter Set**
- Normalized water-leaving radiances (6)
- Aerosol optical thickness
- Atmospheric correction epsilon
- Ångström exponent
- Chlorophyll-a (1)
- Diffuse attenuation coefficient at 490 nm
- SST (near real-time daytime skin temp.)
- Same masks & flags as OC products

- Previous OC Parameter Set      38
- (does not include archived ancillary data &
- quality control fields)
- Current OC Parameter Suite     12
- (does not include archived ancillary data)

## Calibration/Validation Approach

**Apply same cal/val approach as for SeaWiFS**
**Common processing codes**
**Work sensor calibration issues with MCST**
- Solar and lunar calibration analysis and products, e.g., calibration tables, response-vs-scan (RVS), sensor polarization.
**Systematically test algorithms using both SeaWiFS & MODIS for comparison**
- Polarization, BRDF, glint, cloud masking, etc.
- Global time series with regional analyses (clear-water, deep-water, coastal, basin-latitude zones)

## MODIS OC Calibration

- Prelaunch Calibration & Characterization:
- (Santa Barbara Research Center)

- On-Orbit Solar & Lunar Calibration
- (MODIS Characterization Support Team)

- MOBY-based Vicarious Calibration Adjustment
- (D. Clark and OCDP Group)

- SeaWiFS-MODIS Regional & Global Comparisons
- (OCDP Group)

- In-situ/Satellite Match-up Comparisons
- (OCDP Group)

- In Situ Data Collection
- (MODIS Ocean Team)

- Prelaunch data reviewed by
- MCST, OCDP, & MODIS Ocean Team members

- One set of vicarious gains
- for entire MODIS/Aqua data
- record.

- Time-dependent gain factors.

## SeaWiFS Stability

- Monthly views of the moon at ~ 7° phase angle.
- Gradual monotonic degradation primarily in
- NIR bands.

- Global mean deep water Lwn’s with no trends,
- i.e., repeating annual cycles

## MOBY Vicarous Calibration

## MODIS(Aqua)/SeaWiFS Lwn Ratios (N. Pacific):Initial comparison

## MODIS/SeaWiFS Comparisons

- MODIS polarization correction*
- Polarization tables found to be phase-shifted with approximately half the correct amplitude
- BRDF correction (based on Morel et al., 2002)
- Developed for Case 1 waters (mostly open ocean)
- Not accurate in turbid waters
- Error in algorithm found recently
- Testing to continue
- Quality mask & flag thresholds
- Sunglint radiance threshold
- Cloud mask threshold

-  MODIS polarization tables based
- on prelaunch characterization table.
-  SeaWiFS essentially polarization
- insensitive.

## MODIS(Aqua)/SeaWiFS Lwn Ratios (N. Pacific):Correct polarization (corrected phase & magnitude)

- MODIS(Aqua)/SeaWiFS Lwn Ratios (N. Pacific):Correct polarization (corrected phase & magnitude)

- 412 nm atmospheric correction
- problem at high solar zenith angles?

## MODIS/Aqua ReprocessingCompleted in May ‘04 (~ 11⁄2 weeks)

- MCST temporally smoothed calibration tables
- Phase & magnitude corrected polarization tables
- Simple BRDF correction
- OC3 chlorophyll-a algorithm
- Similar to SeaWiFS OC4v4 algorithm

- OCDP Group continues work with MCST to refine on-board lunar & solar calibration analyses.

## SeaWiFS & MODIS 4-Day Deep-Water Chlorophyll Images

**SeaWiFS & MODIS 4-Day Deep-Water Chlorophyll Images**
- 4 day composites, Summer 2002

**0.01-1 mg/m^3**

- SeaWiFS

- MODIS
- (Correct polarization
- phase & amplitude)

## SeaWiFS Lw

**SeaWiFS Lw**
**OCDPS Repro4**

**MODIS/Aqua Lw**
**OCDPS Repro**

## OCDPS Repro4

**OCDPS Repro4**
**OC4 Chlorophyll**

**OCDPS Repro**
**OC3 Chlorophyll**

**SeaWiFS**

**MODIS/Aqua**

## Additional Sensor Calibration Issues

- Temporal stability: long-term and seasonal
- Refine “Response vs. Scan” (RVS) or scan modulation functions
- Minimize mirror-side calibration differences (image banding)
- Detector to detector calibration (striping)

- Analyses to be conducted in collaboration with MCST
- and science community.

## Back Up Slides

## OCDP SST

- SST
- enhanced to allow use of Reynolds OI SST as input
- detailed intercomparison with MODAPS products performed
**exact match** demonstrated at Level-2 (given same input SST)
- required correction of MODAPS code for OISST interpolation error

- MODAPS

- ODPS

-  Only remaining issue is Level-3 quality masking
-  MODAPS approach has been analyzed in detail
-  implementation plans TBD
-   http://seabass.gsfc.nasa.gov/eval/fq.cgi