# Presentation: 185915

## MODIS/Aqua Ocean Reprocessing

- Bryan Franz
- Ocean Biology Processing Group
- MODIS Science Team Meeting
- 22-24 March 2005

## Introduction	

**MODIS/Aqua Ocean Reprocessing 1 completed March 2005.**
**L1A-GEO-L1B-L2 completed less than 1 week (~150X)**
** ****Also completed ****SeaWiFS Reprocessing 5**
**This presentation will cover**
**Remaining issues from initial OBPG processing**
**Changes implemented for this reprocessing**
**Analysis of results**
**Remaining issues & work in progress**
**New products available for evaluation**

## Issues Following Initial OBPG Processing of MODIS/AquaCompleted May 2004

## Issues from Initial ProcessingCompleted May 2004

- Inconsistency in the annual cycle of global water-leaving radiances

**MODIS/Aqua**

**SeaWiFS R4.1**

- Deep-Water - mean of all common bins deeper than 1000 meters

## Issues from Initial Processing

**Issues from Initial Processing**

- Long-term (3% per year) and seasonal (+/- 10%) deviations relative to SeaWiFS R4.1 global trends

**Global Deep-Water nLw Ratio**

**+50%**

**-50%**

- ~ 3**% change/year**

**+10%**

**-10%**

## Issues from Initial Processing

- Differences relative to SeaWiFS R4.1 which increase with latitude or solar zenith angle

**35 North**

**25 North**

**15 North**

**nLw Ratios, Zonal Pacific, 150W-170W**

**+20%**

**-20%**

## Issues from Initial Processing

- Very large differences relative to SeaWiFS R4.1 in global mean aerosol optical thickness retrievals

**MODIS and SeaWiFS Deep-Water AOT Comparison**

**MODIS****/Aqua**

**SeaWiFS**

**0.15**

**0.10**

## Issues from Initial Processing

- Larger deviations in recent months due to out-dated MODIS instrument calibration look-up table (LUT)

- Last SD Measurement
- for Operational LUT

**MODIS/SeaWiFS Deep-Water nLw Ratio**

## Reprocessing Changes

## Changes for 1st Aqua Reprocessing

- Updated instrument calibration
- MCST V5.0.1 equivalent, OBC measurements to Nov 2004.
- Refit by OBPG as single exponential after removal of detector-dependent screen vignetting residuals.

**Before LUT Change**

**After LUT and Other Changes**

## Changes for 1st Aqua Reprocessing

**Changes for 1st Aqua Reprocessing**

- Straylight Masking
- Modeled point-spread function (PSF) indicates significant sensitivity to straylight from adjacent sources.
- 7 x 5 masking around cloud and saturation pixels removes the most significant contamination, fixes AOT discrepancy.

**Before SL Masking**

**After SL Masking**

**MODIS Band 16 PSF**

**MODIS & SeaWiFS Deep-Water AOT Comparison**

**0.15**

**0.10**

## Changes for 1st Aqua Reprocessing

- Changes to atmospheric correction
- Updated relative spectral response (RSR) functions: new Rayleigh tables and band-averaged coefficients.
- Revised Rayleigh pressure correction (M. Wang), to include solar zenith dependence (effect can be significant at high latitudes, for large deviations from standard pressure).

**Deep-Water nLw Ratio**

**40-50N Pacific nLw Ratio**

**Impact of Change on MODIS nLw **

**+1%**

**-10%**

## Changes for 1st Aqua Reprocessing

**Changes for 1st Aqua Reprocessing**

- Enhanced Fresnel correction for Lw normalization
- include reflection/refraction to downwelling irradiance.

**Fresnel Correction, Atmosphere to Ocean**

- Wind = 0 m/s

- Wind = 20 m/s

**M. Wang Model**

## Changes for 1st Aqua Reprocessing

- Morel f/Q correction for Lw normalization
- accounting for non-isotropic sub-surface light field

**Deep Water nLw Ratio**
**MODIS/SeaWiFS**

**After f/Q**

**Southern Pacific**
**MODIS/SeaWiFS**

**Before f/Q**

**+20%**

**  ****0%**

**-20%**

**+50%**

**  ****0%**

**-50%**

## Changes for 1st Aqua Reprocessing

- Morel f/Q correction for Lw normalization
- accounting for non-isotropic sub-surface light field

**After f/Q**

**Before f/Q**

**Residual Scan Dependence in MODIS nLw(443)**

**+2%**

**-4%**

**+10%**

**  ****0%**

**-10%**

## Changes for 1st Aqua Reprocessing

- MOBY data reprocessing, final vicarious calibration
- largest effect in 412 and 551-nm bands

**Deep-Water**

**Coastal**

**Impact of MOBY Change on MODIS nLw**

**+2%**

**+4%**

## Reprocessing Results

**New LUT**
**Straylight rejection**
**RSR and pressure corrections**
**Fresnel**
**f/Q**
**New MOBY vicarious cal**

## Reprocessing Results

**New LUT**
**Straylight rejection**
**RSR and pressure corrections**
**Fresnel**
**f/Q**
**New MOBY vicarious cal**

**Also applied in SeaWiFS Reprocessing 5**

## Results from Reprocessing 1nLw Comparison with In situ

**Reprocessing 1**

**Results from Reprocessing 1****nLw Comparison with *****In situ***

## Results from Reprocessing 1nLw Comparison with In situ

**MODIS/Aqua R1**

**Results from Reprocessing 1****nLw Comparison with *****In situ***

## Results from Reprocessing 1Chlorophyll Comparison with In situ

**MODIS/Aqua R1**

**Results from Reprocessing 1****Chlorophyll Comparison with *****In situ***

## Results for Reprocessing 1

- Consistency in annual cycle is approaching SeaWiFS

**MODIS/Aqua R1**

**SeaWiFS R5**

## Results from Reprocessing 1nLw Comparison to SeaWiFS R5

- Sensor agreement to within 7% for global mean deep-water nLw retrieval.  Better for clear water.
- Some bias & trend is still evident between instruments.

**Initial Processing**

**Reprocessing 1**

**+10%**

**  ****0%**

**-10%**

## Results from Reprocessing 1

**35 North**

**25 North**

**15 North**

**nLw Ratio to SeaWiFS R5, Zonal Pacific, 150W-170W**

**Initial Processing**

**Reprocessing**

**+/- 20%**

**+/- 10%**

**+/- 5%**

**Laitude (Solar Zenith)**

## Results from Reprocessing 1

**Deep-water AOT and Chlorophyll Comparison to SeaWiFS**

**AOT (865)**

**Chlorophyll**

**Solid Line: ****	****MODIS/Aqua R1**
**Dashed Line: ****	****SeaWiFS R5**

**<C****modis****>   = 0.174 mg m****-3**
**<C****seawifs****>  = 0.171 mg m****-3**

## Seasonal Chlorophyll Images

**Seasonal Chlorophyll Images**

**0.01-64 mg m****-3**

**Summer 2004**

**Winter 2004**

**SeaWiFS R5**

**MODIS/Aqua R1**

**Winter 2004**

**Summer 2004**

## Remaining Issues & Work in Progress

- Bias & trends in relative agreement with SeaWiFS
- instrument calibration (SD fit, lunar vs solar, RVS change)
- effect of aerosols on polarization (analysis in progress)
- straylight correction (reduce masking losses)
- apparent earth shine in dark counts
- Residual cross-scan trends
- Residual striping

## Residual Cross-scan Trends

- Global mean residual RVS at +/- 3% in nLw
- Already Level-3 masking at 60° sensor zenith

**nLw(412)**

**nLw(551)**

**+20%**

**-20%**

**+10%**

**-10%**

## Residual RVS & Striping in Red Bands

**nLw(667)**

**nLw(678)**

**+20%**

**-20%**

**+10%**

**-10%**

**   ****0%**

- Fractionally large cross-scan artifacts in red, no explanation yet.

## Residual Striping

- Global mean residual striping at +/- 2% in nLw
- Consistent over life of mission (problem with SD cal?)

**nLw(412)**

**nLw(551)**

**+10%**

**-10%**

**+5%**

**-5%**

## Progress on Striping Corrections

**Progress on Striping Corrections**

- MCST Lunar Analysis ()
- derived by averaging **all** Lunar calibrations on a per-detector basis
- OBPG TOA Analysis (,)
- derived by collecting 20-pixel along-track runs (10 detectors x 2 mirror sides) in clear atmosphere/low polarization/low chlorophyll conditions, correcting for relative change due to atmosphere, and averaging per detector, per mirror-side.

**Red & NIR bands **
**saturate on Moon**

## Effect of OBPG Striping CorrectionnLw 412 nm

**Before Correction**

**After Correction**

## New Productsfor evaluation

## New or Revised Productsimplemented for evaluation

**Carder IPAR & ARP**
-  **ipar ****-**** ***instantaneous photosynthetically available radiation*
-  **arp ****-**** ***instantaneous absorbed radiation by phytoplankton*
**Chlorophyll Fluorescence and Supporting Products**
-  **flh ****-**** ***fluorescence line height*
-  **cfe ****-**** ***chlorophyll fluorescence efficiency*
**Clark Empirical Algorithms**
-  **chl_clark ****-**** ***chlorophyll concentration*
-  **poc_clark ****-**** ***particulate organic carbon*
-  **tsm_clark ****-**** ***total suspended matter*
**Gordon & Balch Calcite**
-  **calcite_2b ****-**** ***calcite concentration, 2-band algorithm*
-  **calcite_3b ****-**** ***calcite concentration, 3-band algorithm*

## New or Revised Productsimplemented for evaluation

**IOP Models**
** ****gsm01  ***- Garver-Siegel-Maritorena Semi-Analytical*
** ****carder  ***- Carder Semi-Analytical*
** ****qaa****	****   ***- Quasi-Analytical Algorithm ****
**IOP-based Products**
** ****Kd_lee ***- Z.P.Lee diffuse attenuation ****

*** **Coming Soon, Thanks to P. Martinolich at  NRL Stennis

## In The Works

**Daily-Average PAR (R. Frouin)**
** ****PAR **- *SeaWiFS PAR updated for MODIS*

## Seasonal Chlorophyll Images

**Seasonal Chlorophyll Images**

**0.01-64 mg m****-3**

**Summer 2004**

**Winter 2004**

**SeaWiFS R5**

**MODIS/Aqua R1**

**Winter 2004**

**Summer 2004**

## Extra Slides

## Residual RVS & Striping in Red Bands

**nLw(667)**

**nLw(678)**

**+10%**

**-10%**

**+5%**

**-5%**

**+20%**

**-20%**

**+10%**

**-10%**

## New or Revised Productsimplemented for evaluation

**Garver-Siegel-Maritorena Semi-Analytical Bio-Optical Model**
-  **chl_gsm01** 		- *chlorophyll concentration*
-  **a_nnn_gsm01** 	- *total absorption*
-  **bb_nnn_gsm01** 	- *total backscatter*
-  **bbp_nnn_gsm01** 	- *particulate backscatter*
-  **aph_nnn_gsm01** 	- *absorption due to phytoplankton*
-  **adg_nnn_gsm01** 	- *absorption due to gelbstof and detrital material*
**Carder Semi-Analytical Bio-Optical Model**
-  **chl_carder** 		- *chlorophyll concentration*
-  **a_nnn_carder** 	- *total absorption*
-  **bb_nnn_carder** 	- *total backscatter*
-  **bbp_nnn_carder**	- *particulate backscatter*
-  **aph_nnn_carder** 	- *absorption due to phytoplankton*
-  **adg_nnn_carder** 	- *absorption due to gelbstof and detrital material*
-  **flags_carder** 		- *product-specific flags*

**nnn** - *sensor wavelength*

## Coming Soon

**Quasi-Analytic Algorithm (Z.P. Lee)**
** ****a_nnn_qaa** 	  - *total absorption*
-  **bb_nnn_qaa** 	  - *total backscatter*
-  **bbp_nnn_qaa**  - *particulate backscatter*
-  **aph_nnn_qaa**  - *absorption due to phytoplankton*
-  **adg_nnn_qaa**  - *absorption due to gelbstof and detrital material*
**IOP-based Diffuse Attenuation (Z.P. Lee)**
** ****Kd_nnn_lee** - *diffuse attenuation at sensor wavelength nnn*

**nnn** - *sensor wavelength*

***Thanks to P. Martinolich at  NRL Stennis***

## On the Subject of Flags

**Each derived product should include tests for:**
- poor or questionable quality, sets the Level-2 **CHLWARN** flag bit
- algorithm failure, sets the Level-2 **CHLFAIL** flag bit
**The failure and warning flags can be masked at Level-3. The binner masking is product independent, all products binned at the same time are masked the same.**
**Additional flags or supporting products *****can be***** associated with a derived product, for QC and evaluation purposes at Level-2.  No impact to binning.**

## Carder Model Product-Specific Flag Definitionflags_carder

**Carder Model ****Product-Specific Flag Definition****flags_carder**

## In situ Match-ups for MODIS/Aqua

- 55% of Radiance Match-ups

**nLw: MODIS/Aqua vs SeaWiFS ****Deep-Water**

**Chlor-a**

**551 vs 555**

**488 vs 490**

**Simulated Center-Wavelength Differences**
**(after band-pass correction)**

- Deep-Water Mean

- Relative to SeaWiFS, the 488 and 551 bands should be elevated at chlorophylls typical of deep water (~0.2 mg/m3).

## MODIS/AquaVariation of Geometry Along-TrackEastern Scan Edge

- Scattering Angle

## Variation of Rayleigh Radiance Along-Track

**Nadir**

**Eastern Edge**

**Western Edge**

**Scattering**
**Angle**

**Rayleigh**
**Radiance**
**412 nm**

**0.05 mW/cm****2**** um sr **
**or ~2% of nLw**

## Cross-Scan Variation of Sensor View ZenithMODIS/Aqua

## Coastal

**Coastal**

## Deep

**Deep**

## Clear

**Clear**

## Slide 52