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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