# Presentation: 413443

## A surface reflectance standard product from LDCM and supporting activitiesJune 07 - Update 

**Principal Investigator**
**Dr. Eric Vermote **
**Geography Dept., **
**University of Maryland**
**Co. P.I. **
**Dr. Chris Justice **
**Geography Dept., **
**University of Maryland**

## Rationale for the research activities

- A Surface Reflectance standard product developed for MODIS provides the basis for a number of higher order land products for global change and applications research
- It is possible to develop an operational robust, globally applicable and fully automated code for integration into the LDCM processing chain and the code made openly available for others to use (e.g. LDCM ground stations).
- The approach has already been testing by the LEDAPS project.

## R and D Areas

**Extend validation/evaluation exercise and develop fully automated procedures**
**Refine the Cloud/Cloud shadow algorithm**
- Establish absolute radiometric calibration to the 2% level
- Operational implementation of the adjacency effect correction
- Coastal water retrievals
- Aerosol type inversion

## Performance of the MODIS C5 algorithms

- To evaluate the performance of the MODIS Collection 5 algorithms, we analyzed 1 year of Terra data (2003) over **127** AERONET sites (**4988** cases in total).
**Methodology:**

- _[http://mod09val.ltdri.org/cgi-bin/mod09_c005_public_allsites_onecollection.cgi](http://mod09val.ltdri.org/cgi-bin/mod09_c005_public_allsites_onecollection.cgi)_

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- Subsets of Level 1B data processed using the standard surface reflectance algorithm

- Reference data set

- Atmospherically corrected TOA reflectances derived from Level 1B subsets

- Vector 6S

- AERONET measurements
- (τaer, H2O, particle distribution)

- If the difference is within ±(0.005+0.05ρ), the observation is “good”.

- comparison

## Validation of MOD09 (1)

- Comparison between the MODIS band 1 surface reflectance and the reference data set.

- The circle color indicates the % of comparisons within the theoretical MODIS 1-sigma error bar:
- green > 80%, 65% < yellow <80%, 55% < magenta < 65%, red <55%.
- The circle radius is proportional to the number of observations.
- Clicking on a particular site will provide more detailed results for this site.

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## Validation of MOD09 (2)

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- Example: Summary of the results for the Alta Foresta site.

**Each bar**: date & time when coincident MODIS and AERONET observations are available
**The size of a bar**: the % of “good” surface reflectance observations

**Scatter plot**: the retrieved surface reflectances vs. the reference data set along with the linear fit results

## Validation of MOD13 (NDVI)

- Comparison of MODIS NDVI and the reference data set for all available AERONET data for 2003. Globally, 97.11% of the comparison fall within the theoretical MODIS 1-sigma error bar (±(0.02 + 0.02VI)).

- green > 80%, 65% < yellow <80%, 55% < magenta < 65%, red <55%

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## The MODIS Vegetation index performances are real

- Maignan and Breon, Personal communication, 2007

## Analysis of the Landsat surface reflectance product performances over AERONET sites are very promising

**Band 3**

**Band 4**

**NDVI**

- DATE.PATH/ROW	AOT    	TIMEDIFF  AERONET SITE
- a2000122.w2p041r036 0.0932345 	15	Rogers_Dry_Lake-001221821.mie
- a2000122.w2p041r037 0.162749 	15 	UCLA-001221823.mie
- a2000170.w2p009r029 0.0449007 	60 	Kejimkujik-001701451.mie
- a2000191.w2p028r035 0.0858729 	30 	Cart_Site-001911659.mie
- a2000247.w2p036r038 0.0365191 	205 	Tucson-002471753.mie
- a2000261.w2p022r039 0.0722956 	14 	Stennis-002611628.mie
- a2000267.w2p048r026 0.0727889 	14 	Saturn_Island-002671842.mie
- a2001155.w2p034r036 0.105914 	29 	Sevilleta-011551737.mie
- a2001216.w2p029r030 0.133025 	14 	Sioux_Falls-012161656.mie
- a2001217.w2p036r025 0.0797376 	188 	Bratts_Lake-012171728.mie
- a2001218.w2p043r028 0.0735507 	254	Rimrock-012181817.mie
- a2001267.w2p034r032 0.0717833 	14 	BSRN_BAO_Boulder-012671730.mie
- a2001278.w2p015r033 0.147011 	15 	GSFC-012781537.mie

## Improvements in the robustness of the 1km aerosol retrieval

- Snow Contamination
- Salt Pan test

## Snow/Thin cloud ContaminationEast coast Winter scenes

- No filtering for Snow/Thin clouds

- Updated Surface reflectance algorithm

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## Salt Pan test /West coast scenes

- Salt Pan test /West coast scenes

- No filtering for salt pan

- Updated Surface reflectance algorithm

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## Borneo scene

- Old Internal cloud: Yellow

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*13.87 C*

*-1.25 C*

*15.39C*

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## Borneo Scene (details)

- Old Internal cloud: Yellow

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- 8.85C to 12C

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## Borneo scene (details)New cloud mask: Directly on the surface reflectance productusing visible anomaly test: Blue-Red/2 >0.03

- Borneo scene (details)New cloud mask: Directly on the surface reflectance productusing visible anomaly test: Blue-Red/2 >0.03

- New Internal cloud: Visible anomaly

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## Borneo Scene with visible anomaly test and additional test for false detection over turbid water band 5 (1.6mic)  threshold 0.03

- New internal cloud: visible anomaly and
- 1.6mic threshold

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## Visible anomaly test fails also over bright surfaces (salt pan) as “expected”

- New internal cloud: visible anomaly and
- 1.6mic threshold

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## Visible anomaly test fails also over bright surfaces (salt pan) as “expected”but a simple thermal test is very efficient to handle thos “false” cloud detection

- New internal cloud: visible anomaly and
- 1.6mic threshold and thermal test

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## Final re-test on Borneo 

- New internal cloud: visible anomaly and
- 1.6mic threshold and thermal test

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## Conclusions 

-  TECHNICAL LEVEL
- An improved algorithm (robustness) for atmospheric correction has been implemented and will be tested in LEDAPS (the previous version was Beta). We take advantage of the high spatial resolution of Landsat (compared to MODIS) to filter out bad aerosol retrievals.
- A consolidated per pixel cloud mask on the surface reflectance product (third pass) is under evaluation. It is relying on the thermal data.
- Cloud shadow algorithm is available and needs to be evaluated on the new per pixel cloud mask.
- RECOMMENDATION
- The surface reflectance product and cloud/cloud shadow mask is now being used routinely by the Land community (MODIS, AVHHR and now Landsat 5/7). It is necessary to make plans to make those data available in the LDCM era.
- FUTURE PLANS
- Aerosol model update and inversion
- Coastal Water