Regional chlorophyll retrieval algorithms for North Sea waters ...€¦ · 12 pin_1 pin_2 pin_3 Pixel Chl conc. [mg/m³] algal_1 algal_2 REV0 REV1 REV2 REV3 REV4 REV5 REV6 REV7 REV8

MERIS & AATSR Symposium * Frascati * 27.09.2005

ENVIRONMENTAL INFORMATICSGEOINFORMATION PRODUCTS

IVM /BROCKMANN CONSULT

Regional chlorophyll retrieval algorithms for North Sea waters: intercomparison

and validation

S. Peters, C. Brockmann, M. Eleveld, R. Pasterkamp, H. Van der Woerd, K. Ruddick, Y.Park, T. Block, R. Doerffer, H. Krasemann, R. Roettgers,

W.Schoenfeld, P. Joergensen, G. Tilstone, V. Martinez-Vicente, G.Moore, K. Soerensen, J. Hokedal, E. Aas

REVAMP IVM/BROCKMANN CONSULT


Regional chlorophyll retrieval algorithms for North Sea waters: intercomparison and validation

REVAMP

Regional Validation of MERIS Chlorophyll Products in North Sea Coastal Waters

In-situ measurements MERIS Data

• Support the monitoring of the eutrophication status of the North Sea• Develop an improved validated chlorophyll product for the North Sea based on MERIS• Parameterise bio-optical models• Extend MERIS validation beyond the ESA validation phase

RegionalProcessing

EU Contract: EGV1-CT-2001-00049

Chlorophyll Atlas




Regional Algorithms

• Different mathematical models– multispectral colour ratios– radiative transfer model inversion

• look-up table technique• neural network technique• matrix inversion

• Different SIOP data sets– Specific Inherent Optical Properties– algorithm calibration– different optical properties– different distribution of concentration ranges

• REVAMP– locally tuned regional algorithms

• combination of math. model and SIOP calibration data set– North Sea wide comparison

• in-situ data, historical data, MERIS dataREVAMP production processor

inversion technique, LUT, common North Sea SIOP dataset

– REVAMP processor using regional calibration SIOPs




Calibration Intercomparison

REVAMPOperationalProcessor(inversion method)

MERIS L2Water leavingreflectances

REVAMP-xChl concentration

Region-x

Region-1BelgianCoast

Region-5German

Bight

Region-7Skagerrak

…….. others

SIOP calibration files




Calibration Intercomparison Study

• Processor: REVAMP operational processor

• 10 different versions of SIOP-calibration files:0 ... operational REVAMP1 ... Belgian Coast SIOPs2 ... Celtic Sea SIOPs3 ... Central North Sea SIOPs4 ... Dutch Coast SIOPs5 ... German Bight SIOPs6 ... Kattegat SIOPs7 ... Skagerrak, OuterOslofjord, Kattegat,North Sea SIOPs8 ... UK Coast SIOPs9 ... West English Channel SIOPs

• 15 MERIS RR products from June – August 20031st Reprocessing 2004 / 2nd reprocessing 2005




Input Data Summary

1 2 3 4 5 6 7 8 9

No DateBelgium Coast Celtic Sea

Central NS

Dutch Coast

German Bight Kattegat

Skag / Oslo F UK Coast

West Engl. Ch.

1 09.06.2003 x x x2 13.06.2003 x x x x3 25.06.2003 x x x4 04.07.20035 07.07.2003 x6 08.07.2003 x7 10.07.2003 x8 13.07.2003 x x x9 14.07.2003 x x x10 14.07.200311 17.07.2003 x12 06.08.2003 x13 09.08.200314 15.09.2003 x x

x x xx




Example: Southern NS & Skagerrak, 20030809




1

23




0

2

4

6

8

10

12

pin_1 pin_2 pin_3

Pixel

Chl c

onc.

[mg/

m³]

algal_1algal_2REV0REV1REV2REV3REV4REV5REV6REV7REV8REV9




Calibration Intercomparison Study

Conclusions from pixels from single images:

Regional algorithms improve Chlorophyll-a estimates

Locally calibrated algorithms perform1) Ok at the calibration locations2) Not as well elsewhere

The alternative (standard) strategy is to build an operationalprocessor based on the best knowledge of SIOPs for the region of application (North Sea).




Algorithm Calibration: For the operational REVAMP processor we used the median of all SIOP values in the REVAMP database

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

350 400 450 500 550 600 650 700 750

wavelength

spec

ific

phyt

opla

nton

\par

ticle

abs

orpt

on

0

0.2

0.4

0.6

0.8

1

1.2

1.4

spec

ific

parti

cle

scat

terin

g / C

DO

M

abso

rptio

n

phytoplankton absorptionparticle absorptionparticle scatteringCDOM absorption




Results: 1: Monthly median and maximum Chlorophyll-a mapsApril 2003




Results: 2: Yearly median and maximum Chlorophyll-a maps 2003

Spring bloomMarch April

June: Coccolithophores

bloom

Phaeocystisbloom

March April

Patchy bloomsOf various

species

Blooms in March and

October




Results: 3: Regional Time series of monthly median and maximum Chlorophyll-a maps 2003




Results: 4: Examples of FRImages processed by ACRI to L2 with CHL-a derived from the REVAMP algorithm




Validation Results: Yearly median CHL-a on regular Dutch monitoring points (visited 1-2 times per month)

Compared with

REVAMP yearly median CHL-a from MERIS RR

The correlation coefficient is approximately 0.93




Validation Results: Comparing time series in one monitoring point(high CHL and low CHL situation)




Validation Results: Comparing transect results using data from the FerryBox project




Providing policy support:Eutrophication problem areas are now defined by the presence of monitoring networks

Satellite results Monitoring network result




Some Conclusions

• The REVAMP Chlorophyll-a estimates validate quite well in most water types (some problems in areas with high sediment concentrations)

• Using local algorithms for Chlorophyll-a retrieval may solve this problem

• There are large discrepancies in the areal extent of eutrophication between OSPAR maps based on monitoring networks and satellite derived Chlorophyll-a estimates

• Maximum Chlorophyll-a maps provide a wealth of information on blooms occurences




Acknowledgements

ESA and ACRI are thanked for MERIS image provision

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

All captains, crews and companies/organisations that have helped us tocollect data on ships of opportunity

The REVAMP Quality Assurance Committee (Mike Rast, Eon O’Mongain and Hartmut Heinrich) have earned our thanks and appreciations for many interesting discussions and for keeping us in line.

We thank the EC for funding this very interesting project

Documents

Regional chlorophyll retrieval algorithms for North Sea waters ...€¦ · 12 pin_1 pin_2 pin_3 Pixel Chl conc. [mg/m³] algal_1 algal_2 REV0 REV1 REV2 REV3 REV4 REV5 REV6 REV7 REV8