revamp: a brief overview case study: chl maps of …institute for environmental studies (ivm) 2...

Institute for Environmental Studies (IVM) 1MERIS User Workshop, Frascati, Nov. 2003 vrije Universiteit amsterdam

REVAMP: a brief overviewREVAMP: a brief overviewCase study: CHL maps of the Dutch Case study: CHL maps of the Dutch coastal zonecoastal zone

Institute for Environmental Studies (IVM)Institute for Environmental Studies (IVM)

Vrije Universiteit, AmsterdamVrije Universiteit, Amsterdam

The NetherlandsThe Netherlands

http://www.vu.http://www.vu.nlnl//ivmivm

Steef Peters, Steef Peters, Reinold Pasterkamp Reinold Pasterkamp & Hans van der & Hans van der Woerd & THE REVAMP TEAM!Woerd & THE REVAMP TEAM!


ContentsContents

1. W*51. W*5 +0.5*t+0.5*t

2. Case Study CHL in Dutch coastal 2. Case Study CHL in Dutch coastal waterswaters

3. Conclusions, outlook, 3. Conclusions, outlook, recommendations and recommendations and acknowledgements acknowledgements


1. W*51. W*5 +0.5*t+0.5*t

1. what1. what

2. who 2. who

3. why3. why

4. where4. where

5. When5. When

6. Half way: some achievements6. Half way: some achievements


1.1. 5*W5*WWhat: REVAMP is an EC FP 5 project aiming at a REgional VAlidation

of Meris chlorophyll Products in North Sea Coastal waters

When: Started at 1 February 2002, REVAMP will continue until 1 February 2005

Why: Eutrophication is an acknowledged problem in North Sea coastal waters

Who: 8 Partners in most of the countries surrounding the North Sea

Where: (North Sea + including part of the English Channel and part of Kattegat/Skagerrak


1.1. WhyWhy


1.1. WhyWhy

OSPAROSPAR

Elevated levels of CHLElevated levels of CHL--a (2a (2--3 fold increase compared to 3 fold increase compared to earlier reports)earlier reports)

Offshore background 2Offshore background 2--4 mg m4 mg m--33

Dutch coast 10 to more than 15 mg mDutch coast 10 to more than 15 mg m--33 continuous continuous elevationelevation

Extended Extended phaeocystis phaeocystis blooms (Nuisance, foam)blooms (Nuisance, foam)


1.1. WhyWhyThe two most important nutrients that are needed for plant growtThe two most important nutrients that are needed for plant growth h

are nitrogen and phosphorus.are nitrogen and phosphorus.

Marine phytoplankton take up nitrogen and phosphorus in a ratio Marine phytoplankton take up nitrogen and phosphorus in a ratio of of about 16:1. Normally nitrogen is the limiting nutrient, but the about 16:1. Normally nitrogen is the limiting nutrient, but the recent recent major reductions in phosphorus inputs has led to a condition whemajor reductions in phosphorus inputs has led to a condition where re phosphorus limitation of phytoplankton production now occurs in phosphorus limitation of phytoplankton production now occurs in

certain coastal areas. certain coastal areas.

This has led to an excess of nitrogen over phosphorus in the This has led to an excess of nitrogen over phosphorus in the coastal waters of some European seas, which can result in an coastal waters of some European seas, which can result in an altered phytoplankton species composition and an enhanced altered phytoplankton species composition and an enhanced

growth of nuisance algae. growth of nuisance algae.

(text ICES)(text ICES)


Plymouth Marine Laboratory (PML)

zzzzz

MUMMPML

DMI

IVM

NIVA/UIO

GKSS/BC

1.1. WhoWho

MUMM (Belgium) : Kevin Ruddick, Youngje Park, Mia Devolder, Sigrid Jans

IVM (Netherlands): Steef Peters, Hans van der Woerd,

Reinold Pasterkamp, Marieke Eleveld

Brockmann Consult (Germany):

Carsten Brockmann, Tom Block

GKSS (Germany): Roland Doerffer, Hajo Krasemann,

Helmut Schiller, Ruediger Roettgers

DMI (Denmark):

Peter Jorgensson

PML (UK): Gavin Tilstone,

Victor Martinez Vicente

Gerald Moore

NIVA (Norway):

Kai Soerensen

Jo Hokedal

Merete Grung

UIO (Norway):

Eyvind Aas


1. 1. WhatWhat: : FinalFinal productproduct

Atlas of the Atlas of the Chlorophyll Chlorophyll distributiondistribution in the in the North Sea North Sea 20022002--20032003

Progress onProgress on: : httphttp://ivm5.://ivm5.ivmivm.vu..vu.nlnl//revamprevamp//

And And soon also onsoon also on::http://projects.http://projects.esaesa--aoao.org/.org/


1. 1. WhereWhere: : North SeaNorth Sea++Data collected during 2003 started in March and finished in September.

22 cruises were undertaken in 6 major areas of the North Sea, Western Channel and Celtic Sea .

There was over 121 days of ship time which yielded approximately 60 MERIS images During most cruises samples for the determination of HPLC Chla, particulate absorption, coloured dissolved organic matter absorption (CDOM), total suspended matter (TSM), back-scatter at 6 wavelengths were determined. In addition, profiles of Ed, Lu, volume scattering function (VSF), absorption-attenuation (ac9) and reflectance spectra were determined on many cruises.

Opportunistic sampling on blue sky days generated far more match ups than cruises of one or more wk duration.

(Gavin Tilstone, REVAMP progress report)


2. Half way: some achievements2. Half way: some achievementsThe project aims to be user driven and has therefore The project aims to be user driven and has therefore

started with the initial user requirements document started with the initial user requirements document (describing also the future requirements for L3 (describing also the future requirements for L3

products)products)

Historic protocols were reviewed and updated (Historic protocols were reviewed and updated (Tilstone Tilstone et et al., TBP)al., TBP)

All historic + 2002 (and part of 2003) data+metadata have All historic + 2002 (and part of 2003) data+metadata have been stored in a webbeen stored in a web--accessible database at MUMM accessible database at MUMM

(Password protected) (MUMM & GKSS)(Password protected) (MUMM & GKSS)

A MERIS processor was built at BC (using Java software) A MERIS processor was built at BC (using Java software) that allows to “plug in” new algorithms quite easily by that allows to “plug in” new algorithms quite easily by

the algorithm providers themselves! (with full access to the algorithm providers themselves! (with full access to flags etc.)flags etc.)


2. Half way: more achievements2. Half way: more achievements1.1. More than 10 new CHL algorithms were devised / More than 10 new CHL algorithms were devised /

(re)calibrated using the historic data set (GKSS, (re)calibrated using the historic data set (GKSS, NIVA/UIO, DMI, IVM, PML) and implemented in the BCNIVA/UIO, DMI, IVM, PML) and implemented in the BC--MERIS processorMERIS processor

2.2. During a special workshop at MUMM criteria were During a special workshop at MUMM criteria were determined to test and select the “best/most robust determined to test and select the “best/most robust etc.” algorithm, initial tests were performed using a etc.” algorithm, initial tests were performed using a separate selection of historic dataseparate selection of historic data

3.3. Inherent optical properties were studied to determine Inherent optical properties were studied to determine the degree ofthe degree of regionalityregionality in the North Sea: preliminary in the North Sea: preliminary conclusion: the variability is too high (and/or the conclusion: the variability is too high (and/or the amount of data is still too low): No specific regions amount of data is still too low): No specific regions could be distinguishedcould be distinguished


2. Half way: to do next2. Half way: to do next

To determine the preferred REVAMP CHL algorithm:To determine the preferred REVAMP CHL algorithm:

Update algorithms to the final versionUpdate algorithms to the final version

Expand the test data set with 2002/2003 observationsExpand the test data set with 2002/2003 observations

Collect all MERIS matchCollect all MERIS match--up spectra to test algorithms up spectra to test algorithms and the overall quality of MERISand the overall quality of MERIS

Make a small selection of test MERIS imagesMake a small selection of test MERIS images

Set up quality indicators for the CHL productSet up quality indicators for the CHL product


3. Case study CHL in Dutch coastal 3. Case study CHL in Dutch coastal waterswaters

A preliminary comparison of two new types of algorithms with theA preliminary comparison of two new types of algorithms with thealgalalgal--2 pigment index2 pigment index

The algorithm by The algorithm by Reinold Pasterkamp Reinold Pasterkamp based on lookup tables based on lookup tables generated from generated from Hydrolight Hydrolight simulationssimulations

This algorithm solves first for a and b and then for the This algorithm solves first for a and b and then for the concentrationsconcentrations

It uses a series of differences of two spectral bands (to compenIt uses a series of differences of two spectral bands (to compensate sate for offset errors)for offset errors)

The algorithm by S. Peters which uses an iterative analytical soThe algorithm by S. Peters which uses an iterative analytical solution lution of the Gordon equation based on spectra that are 0 at of the Gordon equation based on spectra that are 0 at approximately 750 nmapproximately 750 nm


3. Case study CHL in Dutch coastal 3. Case study CHL in Dutch coastal waterswaters

R(0-)’ = the measured reflectance – the measured reflectance at 750 nm.

An iterative solution is required because of the interdependency of the parameters in the sub-algorithms:

TSM and CDOM are determined using Matrix Inversion Techniques,

CHL is determined using a series of band ratios (and a least squares technique (singular value decomposition))

No assumptions are made other than those underlying the Gordon equation

The algorithm is calibrated on historic observations of specific inherent optical properties in the Dutch coastal zone

(0 ) ' * ( 750 )b b

b b

b bR f f at nma b a b

− = −+ +

* * *w TCHL TSM CDOMa a a TCHL a TSM a CDOM= + ⋅ + ⋅ + ⋅ +a*CPC.CPC

TSMBbbb TSMwbb ⋅+= *,


3. Case study CHL in Dutch coastal 3. Case study CHL in Dutch coastal waters: waters: validation of Peters algorithm using 50 complete validation of Peters algorithm using 50 complete

historic spectrahistoric spectra

y = 1.0934x + 0.7933R2 = 0.8436

n=50

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40


3. Case study CHL in Dutch coastal 3. Case study CHL in Dutch coastal waters: waters: Results for 2 September 2003: MERIS AOD


3. Case study CHL in Dutch coastal 3. Case study CHL in Dutch coastal waters: waters: Results for 2 Results for 2 september september 2003: Peters2003: Peters


3. Case study CHL in Dutch coastal 3. Case study CHL in Dutch coastal waters: waters: Results for 2 Results for 2 september september 2003: 2003: PasterkampPasterkamp


3. Case study CHL in Dutch coastal 3. Case study CHL in Dutch coastal waters: waters: Results for 2 Results for 2 septemberseptember 2003: Algal2003: Algal--22


3. Case study CHL in Dutch coastal 3. Case study CHL in Dutch coastal waters: waters: Results for 14 July 2003 (not a match-up image):

MERIS Aerosol Optical Depth



Peters



Pasterkamp



Algal-2 pigment index


3. Case study CHL in Dutch coastal 3. Case study CHL in Dutch coastal waters:waters:

Conclusion: AlgalConclusion: Algal--2 pigment index lowest 2 pigment index lowest valuesvalues

Patterns are very compatiblePatterns are very compatible

Peters CHL results quite noisy due to the use Peters CHL results quite noisy due to the use of bandof band--ratiosratios

Application of all algorithms to MERIS match Application of all algorithms to MERIS match up spectra will give a lot more insight up spectra will give a lot more insight


3. Some general conclusions3. Some general conclusions

There is a nice convergence of patterns in There is a nice convergence of patterns in various types of algorithms: this gives various types of algorithms: this gives confidenceconfidence

Absolute values in the Dutch coastal zone Absolute values in the Dutch coastal zone must be validatedmust be validated

Noise elimination is requested for the MERIS Noise elimination is requested for the MERIS l2 productl2 product


3. Back to REVAMP3. Back to REVAMP

A timing problem may occur: we need the full set of A timing problem may occur: we need the full set of 2003 reprocessed images in early spring 20042003 reprocessed images in early spring 2004

If this is not possible at ESA I would like to suggest If this is not possible at ESA I would like to suggest that ESA issues a “stand alone” atmospheric that ESA issues a “stand alone” atmospheric processor like SEADAS processor like SEADAS

This would also benefit scientific research if the This would also benefit scientific research if the program can be tuned (not modified) to specific program can be tuned (not modified) to specific user wishes such as: process all pixels as if they user wishes such as: process all pixels as if they were casewere case--2 turbid water!2 turbid water!


3. Final remarks3. Final remarks

MERIS is the only instrument present that can MERIS is the only instrument present that can resolve CHL in this type of turbid watersresolve CHL in this type of turbid waters

partly due to the presence of a 705 nm band partly due to the presence of a 705 nm band (please do not change this!!)(please do not change this!!)

The image quality is The image quality is exellentexellent: very high : very high sensitivity, but somewhat noisysensitivity, but somewhat noisy


3. Acknowledgements3. Acknowledgements

ESA, Brockmann Consult and ACRI are thanked for MERIS image provision

ESA is thanked for bringing us an extremely usefull, well calibrated and very sensitive instrument, and for hosting and organising the MERIS validation and user community meetings on many occasions

All REVAMP colleagues/comrades are gratefully acknowledged for their contributions to the project

We thank the EC for funding this very interesting project

revamp: a brief overview case study: chl maps of …institute for environmental studies (ivm) 2...

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