chapter 8 satellite data of ocean color remote sensing of ocean color instructor: dr. cheng-chien...

Chapter 8Chapter 8

Satellite Data of Ocean ColorSatellite Data of Ocean ColorRemote Sensing of Ocean ColorInstructor: Dr. Cheng-Chien Liu

Department of Earth Sciences

National Cheng-Kung University

Last updated: 27 April 2003

8.1 Introduction8.1 Introduction

OutlineOutline• Level

• Type

• Format

• Parameters

• Name convention

• Access

8.1 Introduction (cont.)8.1 Introduction (cont.)

LinksLinks• CZCS

Getting Started with Coastal Zone Color Scanner (CZCS) Datahttp://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/CZCS_Starter_kit.html

• SeaWiFSSummary and Samples of SeaWiFS Operational Data Products

http://seawifs.gsfc.nasa.gov/SEAWIFS/SOFTWARE/DATA_PRODUCTS.html

SeaWiFS Archive Product Specifications - version 4.1 - updated October 2002 http://seawifs.gsfc.nasa.gov/SEAWIFS/SOFTWARE/specs.4.1.pdf

8.1 Introduction (cont.)8.1 Introduction (cont.)

Links (cont.)Links (cont.)• MODIS

An overview of the MODIS Ocean Data productshttp://modis-ocean.gsfc.nasa.gov/dataprod.html

Ocean product informationhttp://daac.gsfc.nasa.gov/daac-bin/whom/infoscript.pl?cfg=MODIS/ocean/info.cfg

8.2 Data Level8.2 Data Level

Raw dataRaw data• Data in their original packets, as received from

the observer

Level 0Level 0• Raw instrument data at original resolution,

time ordered, with duplicate packets removed

8.2 Data Level (cont.)8.2 Data Level (cont.)

Level 1ALevel 1A• Reconstructed unprocessed instrument/payload data

at full resolution; any and all communications artifacts (e.g. synchronization frames, communications headers) removed

• Primary output of the L1A process containsUnconverted radiances for all detectors at all sources; Decommutated instrument engineering and memory information; Spacecraft ancillary data; EOS standard metadata; Granule-specific metadata; Data quality information.

8.2 Data Level (cont.)8.2 Data Level (cont.)

Level 1B Level 1B • Level 1A data that have been processed to sensor

units and radiometrically corrected and geolocatedOnly Channels 1 and 2 (primary use is land/cloud boundaries) have

250-m resolution, Channels 3-7 (primary use is land/cloud properties) have 500-m resolution, and the rest have 1-km resolution.

• This MODIS data product consists of: 250 m bands calibrated data aggregated to 1 km resolution and their

uncertainties 500 m bands calibrated data aggregated to 1 km resolution and their

uncertainties 1 km bands calibrated data and their uncertainties Subset of geolocation dataQuality Assurance and Instrument Status Metadata.

8.2 Data Level (cont.)8.2 Data Level (cont.)

Level 2Level 2• Derived geophysical variables at the same

resolution and location as the Level 1 source data.

Level 3 Level 3 • Variables mapped on uniform space-time grid

scales, usually with some completeness and consistency.

Fig. 8.2.1 An example of MODIS MODOCL2 Browse Image and Coordinates for 2003-APR-21 03:25:00 to 2003-APR-21 03:30:00Source: http://acdisx.gsfc.nasa.gov/data/dataset/MODIS/03_Ocean/01_Level2/index.html

Fig 8.2.1Fig 8.2.1

8.2 Data Level (cont.)8.2 Data Level (cont.)

Level 4 Level 4 • Model output or results from analyses of lower

level data (i.e., variables derived from multiple measurements).

8.3 Data Type8.3 Data Type

GAC (Global area coverage)GAC (Global area coverage) LAC (Local area coverage)LAC (Local area coverage) BrowseBrowse

8.4 Data Format: HDF8.4 Data Format: HDF

HDFHDF• A self-describing data format

All of the information necessary to examine the data in an HDF file is contained within the file

• Developed by the National Center for Supercomputing Applications (NCSA) at the University of Illinois

• To help scientists reduce the time they were spending trying to convert data sets to familiar formats and instead have more time available for actually analyzing data

8.4 Data Format: HDF (cont.)8.4 Data Format: HDF (cont.)

AdvantagesAdvantages• portability to multiple machines (i.e. platform

independent)

• self documented files

• efficient storage of and access to large data sets

• capability of storing multiple data structures or types within the same file

• extensibility for future enhancements

8.4 Data Format: HDF (cont.)8.4 Data Format: HDF (cont.)

Example of HDF format:Example of HDF format:

8.5 Parameters8.5 Parameters

IntroductionIntroduction• Three categories

Ocean color 36 parameters, six sub-groups

Optical properties (12=5+7) Aerosol models (2) Fluorescence (3) Concentrations (8) Chlorophyll (3) Absorption coefficients (8=3+5)

Sea surface temperature (SST) 4 parameters

SST bulk or skin temperature of the ocean during the day or at night (4)

Ocean productivity

8.5 Parameters (cont.)8.5 Parameters (cont.)

Introduction (cont.)Introduction (cont.)• Resolution

Each of the forty (40) ocean color and SST parameters is associated with Products that have several time and spatial resolutions

• Temporal resolutionLevel 2 data are 5-minute granuleslevel 3 data are associated with daily, 8-daily and monthly data

• Spatial resolution (4)1 km, 4.6-km, 36-km or 1-degreeOcean productivity consists of two Level 4 products: weekly and yearly

ocean primary productivity at 5-km spatial resolution

8.5 Parameters (cont.)8.5 Parameters (cont.)

Optical propertiesOptical properties• 12 parameters

Tau Aerosol (at 865 microns)Epsilon (765/865)Epsilon for Clear Water (at 531 microns)Instantaneous PARDiffuse Attenuation (K 490)Normalized Water-leaving Radiances (in seven bands from

412 to 678 microns)

8.5 Parameters (cont.)8.5 Parameters (cont.)

Optical properties (cont.)Optical properties (cont.)• Tau aerosol, 865

865 atmospheric correction LWN

DimensionlessOnly provided for cloud-free pixels (with Sun glitter below

a threshold)All valid pixels are outside a distance threshold from land

8.5 Parameters (cont.)8.5 Parameters (cont.)

Optical properties (cont.)Optical properties (cont.)• Epsilon 78 (765/865)

78 765/865

Dimensionless (0 ~ 1.5)

8.5 Parameters (cont.)8.5 Parameters (cont.)

Optical properties (cont.)Optical properties (cont.)• Epsilon for clear water clearwater

clearwater LWN(531)/ LWN(667)

DimensionlessObjectives

Estimate aerosol iron content Flag suspicious LWN retrievals

Check on the Angstrom exponent

8.5 Parameters (cont.)8.5 Parameters (cont.)

Optical properties (cont.)Optical properties (cont.)• Instantaneous PAR, Ed,PAR

Photosynthetically Available Radiation (PAR)The total downwelling flux of photons (0-, 400-700nm) mW cm-2 micron-1 sr-1

Objectives of Ed,PAR

photosynthetic rate of growth of phytoplankton primary ocean production. LWN Rrs Chl-a

8.5 Parameters (cont.)8.5 Parameters (cont.)

Optical properties (cont.)Optical properties (cont.)• Diffuse attenuation K490

Unit: m-1

AOPK490 = K490 (,z)

8.5 Parameters (cont.)8.5 Parameters (cont.)

Optical properties (cont.)Optical properties (cont.)• Normalized water-leaving radiances LWN

7 bands (412, 443, 490, 531, 551, 667, 678 nm)Unit: mW cm-2 micron-1 sr-1

LWN Rrs Chl-a primary productivity

The fundamental parameters for recovering most of the MODIS ocean products

8.5 Parameters (cont.)8.5 Parameters (cont.)

Aerosol ModelsAerosol Models• Two models

atmospheric correction removal of aerosols (difficult)A set of candidate aerosol models.

aerosol size distribution, aerosol index of refraction, assumption of spherical particle…

Two models from 16 candidate models

8.5 Parameters (cont.)8.5 Parameters (cont.)

Fluorescence Fluorescence • Mechanism of light reaction

• ApplicationEstimate chlorophyll concentrations and primary

productivity

8.5 Parameters (cont.)8.5 Parameters (cont.)

Fluorescence (cont.)Fluorescence (cont.)• Fluorescence baseline

Unit: mW cm-2 micron-1 sr-1

linearPlaces on either side of the fluorescence peak. Created from

Channel 13: LWN(667) and Channel 15: LWN(748)

8.5 Parameters (cont.)8.5 Parameters (cont.)

Fluorescence (cont.)Fluorescence (cont.)• Fluorescence line height (FLH)

The intensity of Channel 14: LWN(678) above the baseline

Unit: mW cm-2 micron-1 sr-1

Solar-stimulated chlorophyll fluorescence current photophysiology of phytoplankton estimate primary productivity

8.5 Parameters (cont.)8.5 Parameters (cont.)

Fluorescence (cont.) Fluorescence (cont.) • Fluorescence efficiency (FE)

DimensionlessQuantifies the level of photosynthesis by phytoplankton

8.5 Parameters (cont.)8.5 Parameters (cont.)

Application of FLH and FEApplication of FLH and FE• FLHChl• FEphotosynthesislevels of nutrient availability

• Fig. 8.5.1 Top vortex spinning counterclockwise draw nutrient-

rich water upwardBottom vortex spinning clockwise force water

downward

Fig. 8.5.1 FLH and FE from the northwestern portion of the Arabian Sea, collected by MODIS on Dec. 2, 2000. Source: http://modis.gsfc.nasa.gov/about/modis_brochure.pdfImage credit: MODIS Ocean Team/Ocean Fluorescence Product, Mark Abbott, Principal Investigator, Oregon State University.

Fig. 8.5.1Fig. 8.5.1

8.5 Parameters (cont.)8.5 Parameters (cont.)

ConcentrationsConcentrations• 8 parameters

CZCS pigmentTotal pigment - case 1Suspended Solids ConcentrationPigment concentration in coccolith bloomsCoccolith concentrationCalcite concentrationPhycoerythrobilin (PEB)Phycourobilin (PUB)

8.5 Parameters (cont.)8.5 Parameters (cont.)

Concentrations (cont.)Concentrations (cont.)• CZCS pigment

CZCS pigment concentration The sum of chlorophyll-a and associated degradation products.

Unit: mg m-3

Based primarily on methods and algorithms developed for the CZCS program and refined and adapted to the MODIS bands

8.5 Parameters (cont.)8.5 Parameters (cont.)

Concentrations (cont.) Concentrations (cont.) • Total pigment - case 1

The sum of chlorophyll a and phaeopigment concentration Case 1 waters: optical properties are dominated by chlorophyll and associated

covarying detrital pigments Case 2 waters: optical properties which may not covary with chlorophyll.

Other substance, such as gelbstoff, suspended sediments, coccolithophores, detritus and bacteria, change optical properties as well

Unit: mg m-3

8.5 Parameters (cont.)8.5 Parameters (cont.)

Concentrations (cont.)Concentrations (cont.)• Suspended Solids Concentration

Ocean suspended sediments analysis of complex bio-optical properties of coastal and estuarine regions/environments

Unit: mg m-3

Ocean substance concentrations productivity global biogeochemical models global climate models

8.5 Parameters (cont.)8.5 Parameters (cont.)

Concentrations (cont.)Concentrations (cont.)• Pigment concentration in coccolith blooms

Unit: mg m-3

Coccolithophores Small marine phytoplankton Form external calcium carbonate scales having diameters of a few microns and

a thickness of 250 to 750 nm The main source of calcium carbonate on Earth An important part of the biogenic carbon cycle

Fig. 8.5.2 Two side-views of coccoliths.Source: http://www.soes.soton.ac.uk/staff/tt/eh/coccoliths.html

Fig. 8.5.2Fig. 8.5.2

Fig. 8.5.3 Coccoliths in the Celtic SeaSource: http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/PIA03441.jpg

Fig. 8.5.3Fig. 8.5.3

8.5 Parameters (cont.)8.5 Parameters (cont.)

Concentrations (cont.)Concentrations (cont.)• Coccolith concentration

This is the detached coccolith concentrationUnit: 1/m3

8.5 Parameters (cont.)8.5 Parameters (cont.)

Concentrations (cont.)Concentrations (cont.)• Calcite concentration

This is the estimated calcite concentration due to coccolithsUnit: mg m-3 of calcium carbonate

8.5 Parameters (cont.)8.5 Parameters (cont.)

Concentrations (cont.) Concentrations (cont.) • Phycoerythrobilin (PEB)

Unit: mg m-3

Phycoerythrins (藻紅素 ) phycourobilin-rich (PUB) phycoerythrins phycoerythrobilin-rich (PEB) phycoerythrins

The PUB and PEB parameters are retrieved by a sequential-convergent-iteration method, which uses five independent bands

8.5 Parameters (cont.)8.5 Parameters (cont.)

Concentrations (cont.) Concentrations (cont.) • Phycourobilin (PUB)

Unit: mg m-3

8.5 Parameters (cont.)8.5 Parameters (cont.)

ChlorophyllChlorophyll• Significance

A key input to the primary ocean production productTo trace oceanographic currents, jets, and plumes

Fig. 8.5.4 Eddies off the Queen Charlotte IslandsSource: http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/QueenCharlotte_S2002164.jpg

Fig. 8.5.4Fig. 8.5.4

8.5 Parameters (cont.)8.5 Parameters (cont.)

Chlorophyll (cont.)Chlorophyll (cont.)• Chlorophyll MODIS

Unit: mg m-3

The concentration of Case 1 chlorophyll in sea water Derived using the Clark 3 or 4-band algorithm

8.5 Parameters (cont.)8.5 Parameters (cont.)

Chlorophyll (cont.)Chlorophyll (cont.)• Chlorophyll-a (SeaWiFS)

Using the standard SeaWiFS "OC2" algorithmIt contains ocean chlorophyll a pigment concentration for

Case 1 waters and Case 2 watersUnit: mg m-3

8.5 Parameters (cont.)8.5 Parameters (cont.)

Chlorophyll (cont.)Chlorophyll (cont.)• Chlorophyll-a (semi-analytic)

Using multiple bands in an analytic modelIt contains ocean chlorophyll a pigment concentration for

Case 1 waters and Case 2 watersUnit: mg m-3

8.5 Parameters (cont.)8.5 Parameters (cont.)

AbsorptionAbsorption• Absorbed radiation by phytoplankton (ARP)

Averaged over the first optical depthUnit: mW cm-2 micron-1 sr-1

Critical for calculation of fluorescence efficiency (FE)

8.5 Parameters (cont.)8.5 Parameters (cont.)

AbsorptionAbsorption• Gelbstoff absorption coefficient

ag

Unit: m-1

It is operationally defined as a of the material that can fit through a 0.2 micron filter

It is also known as yellow substance or colored dissolved organic material (CDOM) absorption

8.5 Parameters (cont.)8.5 Parameters (cont.)

AbsorptionAbsorption• Chlorophyll-a absorption

ac

Unit: m-1

8.5 Parameters (cont.)8.5 Parameters (cont.)

AbsorptionAbsorption• Total absorption

Total absorption includes absorption due to water, phytoplankton, detritus and gelbstoff

Wavelengths: 412, 433, 488, 531 and 551 nmValid data exist only for ocean cloud-free pixelsUnit: m-1

8.5 Parameters (cont.)8.5 Parameters (cont.)

Sea Surface Temperature (SST)Sea Surface Temperature (SST)• IR radiometers

• 11-micron bands and the 4 micron bandsSST for day data, 11 microns (D1)SST for day data, 4 microns (D2)

contamination by sun glitter during the day

SST for night data, 11 microns (N1)SST for night data, 4 microns (N2)

8.6 Name convention8.6 Name convention

L1B and L2 filesL1B and L2 files• <ESDT>.A<start

dataday>.<hhmm>.<vvv>.<prod time>.hdf

8.6 Name convention (cont.)8.6 Name convention (cont.)

L3 and L4 filesL3 and L4 files• <ESDT>.<parameter>.ADD<start

dataday>.<vvv>.<prod time>.hdfwhere

<ESDT> is the Earth Science Data Type (see below) <start dataday> is the starting data day in the form yyyyddd <vvv> is the collection version, using three digits (e.g., 004) <prod time> is the production time in the form yyyydddhhmmss <parameter> is the parameter name (see Table 11 : MODIS Ocean Parameters) yyyy = year ddd = day of year hh = hour mm = minute ss = seconds

8.6 Name convention (cont.)8.6 Name convention (cont.)

MODIS Ocean ESDT DefinitionsMODIS Ocean ESDT Definitions• L1b ESDT: MOD021KM

• L2 Ocean Color ESDT's:MODOCL2

MODOCL2AMODOCL2BMODOCQC

• L2 Sea Surface Temperature (SST) ESDT's:MOD28L2

MOD28QC

8.6 Name convention (cont.)8.6 Name convention (cont.)

MODIS Ocean ESDT Definitions (cont.)MODIS Ocean ESDT Definitions (cont.)• L3 and L4 ESDT's:

binned files (ISEAG projection)MOD<xx><C><##>

<xx> represents: OC: Ocean Color (L3)

27: Primary Production (L4)28: SST (L3)OQ: Ocean Color QC products (L3)SQ: SST QC products (L3)

<C> represents the file type: D: daily 

W: weekly M: monthlyN: yearly (L3 only)Y: yearly (L4 only)HV: annual carbon, export carbon, and new nitrogen production (L4 only)

<##> is the parameter number (01-36) for Ocean Color only and null otherwise

8.6 Name convention (cont.)8.6 Name convention (cont.)

MODIS Ocean ESDT Definitions (cont.)MODIS Ocean ESDT Definitions (cont.)• L3 and L4 ESDT's (cont.):

L3 map files (carte platte projection) MO<rr><q><C><##>

<rr> is the resolution: 1D =  one degree

04 =  4.88 km36 = 39 km

<q> is the statistic that was mapped:   M: mean

    N: number of pixels summed    S: standard deviation    F: common flags    Q: quality    1: flag byte 1    2: flag byte 2    3: flag byte 3

<C> and <##> see definition for L3 binned files (above)

8.6 Name convention (cont.)8.6 Name convention (cont.)

MODIS Ocean ESDT Definitions (cont.)MODIS Ocean ESDT Definitions (cont.)• L3 and L4 ESDT's (cont.):

L4 map files (carte platte projection)MO<cc><p><b><t><f>

<cc> is the model class:    AP: semi-analytical primary production model

   SP: statistical primary production model <p> is the temporal resolution:

   W: weekly (AP & SP)   Y: yearly (SP only)

<b> is the spatial resolution:    A: 5 km

   B: 39 km   1: one degree

8.6 Name convention (cont.)8.6 Name convention (cont.)

MODIS Ocean ESDT Definitions (cont.)MODIS Ocean ESDT Definitions (cont.)• L3 and L4 ESDT's (cont.):

MO<cc><p><b><t><f> (cont.) <t> is the field type:

   M: mean   S: standard deviation (SP chl only)   W: number of weeks   N: number of observations   F: quality map

<f> is the field identifier:   1: Behrenfeld/Falkowski productivity index (AP only)

  2: Howard/Yoder/Ryan productivity index (AP only)  E: photosynthetically available radiation (AP only)  D: mixed-layer depth (AP only)  P: annual empirical primary production (SP only)  N: annual empirical new production (SP only)  X: annual empirical export production (SP only)  C: running annual chlorophyll mean (SP only)

8.6 Name convention (cont.)8.6 Name convention (cont.)

MODIS Ocean ESDT Definitions MODIS Ocean ESDT Definitions (cont.)(cont.)• L3 and L4 ESDT's (cont.):

Only the following 78 combinations are possible for L4 maps:

MOAPW<b>M1, MOAPW<b>M2, MOAPW<b>ME, MOAPW<b>MD,MOAPW<b>N1, MOAPW<b>N2, MOAPW<b>F1, MOAPW<b>F2,MOAPY<b>M1, MOAPY<b>M2, MOAPY<b>ME, MOAPY<b>MD, MOAPY<b>N1, MOAPY<b>N2, MOAPY<b>F1, MOAPY<b>F2, MOSPY<b>MP, MOSPY<b>MN, MOSPY<b>MX, MOSPY<b>MC, MOSPY<b>FP, MOSPY<b>FN, MOSPY<b>FX, MOSPY<b>FC, MOSPY<b>NC, MOSPY<b>SC.  

• metadatafilename.met

where filename is the corresponding level 2, 3, or 4 filename, as above.

8.7 Data access8.7 Data access

GSFC Earth Sciences Distributed Active GSFC Earth Sciences Distributed Active Archive Center (DAAC) Archive Center (DAAC) http://daac.gsfc.nasa.gov/http://daac.gsfc.nasa.gov/• Ocean color http://daac.gsfc.nasa.gov/oceancolor/

CZCS http://daac.gsfc.nasa.gov/data/dataset/CZCS/

OCTS http://daac.gsfc.nasa.gov/data/dataset/OCTS/index.html

SeaWiFS http://daac.gsfc.nasa.gov/data/dataset/SEAWIFS/

MODIS http://mqabi.gsfc.nasa.gov/ http://acdisx.gsfc.nasa.gov/data/dataset/MODIS/index.html