Sea-Viewing Wide Field-of-View Sensor Level 1A Data
Entry ID:
gov.noaa.class.SW_L1
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Summary
ABSTRACT: This data set consists of satellite measurements of global and regional ocean color data obtained by the Sea-viewing Wide Field-of-view Sensor (SeaWIFS), in orbit on the OrbView-2 (formerly SeaStar) platform. The concentration and predominant identity of substances and particles in the euphotic (lighted) zone of the upper ocean influences the apparent color of the ocean, ... which can range from deep blue to varying shades of green and ruddy brown. Living phytoplankton (which contain chlorophyll and associated photosynthetic pigments), inorganic sediments, detritus (particulate organic matter), and dissolved organic matter all contribute to the color of the ocean. SeaWiFS acquires approximately 15 pole-to-pole orbital swaths of data per day, and approximately 90% of the ocean surface is scanned every two days. The file's content consists of raw radiance counts from eight bands (six in visible and two in near infrared spectrum), calibration data, navigation data, instrument telemetry, and selected spacecraft telemetry.
PURPOSE: The purpose of SeaWiFS data is to examine oceanic factors that affect global change and to assess the oceans' role in the global carbon cycle, as well as other biogeochemical cycles, through a comprehensive research program. SeaWiFS data are being used to help clarify the magnitude and variability of chlorophyll and primary production by marine phytoplankton, and to determine the distribution and timing of spring blooms, i.e., the time of highly abundant growth.
SUPPLEMENTAL INFORMATION: Research and monitoring programs are generally interested in the live phytoplankton biomass and the suspended sediment concentration. The chlorophyll algorithms for SeaWiFS provide a relationship between SeaWiFS bands and standard measurements of chlorophyll for live phytoplankton biomass. For sediment concentrations, a measure of scatter provides the best information. At present, experimental backscattering algorithms exist, additional work needs to be done to validate these algorithms. As an alternative, using the remote sensing reflectance for bands that are most sensitive to scatter (and least sensitive to absorption), provides the best characterization of suspended sediments. The current turbidity product is the remote sensing reflectance for band 5 (555 nm). It provides a good measure of turbidity related to sediment over a range of water clarity and provides a measure of the sediment load in the water. (In the engineering community, "turbidity" is measured by an instrument called a nephelometer, which is designed only to measure the relative scattering in units called NTU's, nephelometric turbidity units. In oceanography, turbidity is a catch-all term for poor water clarity or visibility. Visibility, as measured with a Secchi disk, is influenced by absorption, but driven mostly by the sediment load. To confuse this issue, water clarity is based on the diffuse light attenuation, which is strongly influenced by absorption as well as scattering, and efforts are being made to determine attenuation coefficients for SeaWiFS.) Chlorophyll-related pigments have little influence on the reflectance at 555 nm. Because of the low absorption by water, band 5 is extremely sensitive to changes in sediment concentration. (Certain phytoplankton groups, such as coccolithophores, are highly scattering, so they produce strong signals in this band). Under extremely high pigment loads (especially dissolved pigments and detrital, non-algal, pigments), band 5 is less effective, because the absorption is a significant part of the signal, potential causing a reduction in the reflectance. Because of the low absorption by water, band 5 can "see" the bottom in relatively clear water. In very clear water, it can detect sand bottom in 20-30 m. In areas where turbidity events are common, the bottom signal would be the minimum reflectance observable. SeaWiFS band 6 (670 nm) is less sensitive to dissolved and detrital pigments, and does not detect the bottom in more than ~6 m, but does not provide the sensitivity of band 5 for clearer water. Trials have been made of algorithms that determine backscatter. Ultimately, the calculated backscatter will be the best method of describing turbidity. Several factors determine water clarity: absorption due to live phytoplankton, absorption due to dissolved pigments, absorption due to detrital pigments, and scattering due to particulates (mostly inorganic sediments).
CURRENTNESS REFERENCE: upon processing
SPATIAL DATA ORGANIZATION INFORMATION
Direct Spatial Reference: Raster
Raster Object Type: Swath
Free for users covered by CoastWatch contract for online access. For delivery on physical media, users are responsible for the cost of the physical media and production and delivery of the product.
Geographic Coverage
Spatial coordinates
| N: 75.0 |
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S: 13.0 |
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E: -42.0 |
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W: -175.0 |
Data Set Citation
Temporal Coverage
Location Keywords
Science Keywords
ISO Topic Category
Platform
Instrument
Project
Quality
ATTRIBUTE ACCURACY REPORT: Ocean Color values are accurate to within 10 percent. NOAA CoastWatch performs validation of the data through buoy match-ups or other in situ measurements for adjusting processing algorithms as necessary. Chlorophyll values (.001 - 64.767 micrograms per liter) in GeoTIFFs are scaled to 1 to 100.
LOGICAL CONSISTENCY REPORT: tbd
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COMPLETENESS REPORT: tbd
HORIZONTAL POSITIONAL ACCURACY REPORT: Ocean Color products are generally within 1000 meters.
LINEAGE/PROCESS STEP:
PROCESS DESCRIPTION: SeaWiFS Data Analysis System (SeaDAS) module sw101 creates SeaWiFS Level 1A data by appending the following to SeaWiFS Level 0 data (raw radiances counts from all bands as well as spacecraft and instrument telemetry) from a single orbit: calibration data; navigation data; instrument telemetry; and selected spacecraft telemetry. This data product is packaged as one physical HDF file. This processing occurs at GeoEye within 1-4 hours of data collection.
SOURCE USED CITATION ABBREVIATION: SW_L0
PROCESS DATE: Not complete
SOURCE PRODUCED CITATION ABBREVIATION: SW_L1
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: GeoEye .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: NASA/GSFC/EOS > Earth Observing System, Goddard Space Flight Center, NASA .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: GeoEye (formerly ORBIMAGE, Inc) .
TITLE: SeaWIFS Level 0 data .
TITLE: Sea-Viewing Wide Field-of-View Sensor Level 1A Data . Unpublished material .
PUBLICATION DATE: 1997-09-01.
ONLINE LINKAGE: http://coastwatch.noaa.gov/seawifs_ocolor_overview.html .
ONLINE LINKAGE: http://oceancolor.gsfc.nasa.gov/SeaWiFS/ .
ONLINE LINKAGE: http://www.class.noaa.gov/nsaa/products/search?sub_id=0&datatype_fa... .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: GeoEye .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: NASA/GSFC/EOS > Earth Observing System, Goddard Space Flight Center, NASA .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: GeoEye (formerly ORBIMAGE, Inc) .
TITLE: SeaWIFS Level 0 data .
TITLE: Sea-Viewing Wide Field-of-View Sensor Level 1A Data . Unpublished material .
PUBLICATION DATE: 1997-09-01.
ONLINE LINKAGE: http://coastwatch.noaa.gov/seawifs_ocolor_overview.html .
ONLINE LINKAGE: http://oceancolor.gsfc.nasa.gov/SeaWiFS/ .
ONLINE LINKAGE: http://www.class.noaa.gov/nsaa/products/search?sub_id=0&datatype_fa... .
TYPE OF SOURCE MEDIA: Level 0 satellite data .
SOURCE CURRENTNESS REFERENCE: ground condition .
SOURCE CITATION ABBREVIATION: SeaWIFS_L0 .
SOURCE CONTRIBUTION: Raw satellite data from which level 1a dataset is derived. At level 0 there are two spatial resolutions - either LAC (Local Area Coverage), which is 1.1 km at nadir, or GAC (Global Area Coverage), which is 1.1 km resolution but with pixels spaced at 4.4 km intervals. The LAC dataset is used for level 2 processing in CoastWatch.
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: GeoEye .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: NASA/GSFC/EOS > Earth Observing System, Goddard Space Flight Center, NASA .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: GeoEye (formerly ORBIMAGE, Inc) .
TITLE: SeaWIFS Level 0 data .
TITLE: Sea-Viewing Wide Field-of-View Sensor Level 1A Data . Unpublished material .
PUBLICATION DATE: 1997-09-01.
ONLINE LINKAGE: http://coastwatch.noaa.gov/seawifs_ocolor_overview.html .
ONLINE LINKAGE: http://oceancolor.gsfc.nasa.gov/SeaWiFS/ .
ONLINE LINKAGE: http://www.class.noaa.gov/nsaa/products/search?sub_id=0&datatype_fa... .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: GeoEye .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: NASA/GSFC/EOS > Earth Observing System, Goddard Space Flight Center, NASA .
LINEAGE/SOURCE INFORMATION:
ORIGINATOR: GeoEye (formerly ORBIMAGE, Inc) .
TITLE: SeaWIFS Level 0 data .
TITLE: Sea-Viewing Wide Field-of-View Sensor Level 1A Data . Unpublished material .
PUBLICATION DATE: 1997-09-01.
ONLINE LINKAGE: http://coastwatch.noaa.gov/seawifs_ocolor_overview.html .
ONLINE LINKAGE: http://oceancolor.gsfc.nasa.gov/SeaWiFS/ .
ONLINE LINKAGE: http://www.class.noaa.gov/nsaa/products/search?sub_id=0&datatype_fa... .
TYPE OF SOURCE MEDIA: level 1a satellite data .
SOURCE CURRENTNESS REFERENCE: upon processing .
SOURCE CITATION ABBREVIATION: SW_L1 .
SOURCE CONTRIBUTION: SeaWIFS level 1a dataset ready for processing into Ocean Color dataset.
Access Constraints
ACCESS CONSTRAINTS: SeaWiFS L1A data is accessible to only those covered by CoastWatch contract. For more information contact Richard Stumpf via email Richard.Stumpf@noaa.gov.
DISTRIBUTION LIABILITY: Disclaimer - While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.
Use Constraints
Publications of research results utilizing these data must acknowledge the SeaWiFS Project and the Ocean Biology Processing Group (OBPG) at the NASA Goddard Space Flight Center, Greenbelt, MD, USA.
Ancillary Keywords
Data Set Progress
Data Center
Distribution
Distribution Format:
HDF HDF4.1r4
Fees:
Please See Summary
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Personnel
HENG
GU
Role:
TECHNICAL CONTACT
Phone:
(301) 763-8209 x 347
Email:
Heng.Gu at noaa.gov
Contact Address:
5200 Auth Rd Rm 601
City:
Camp Springs
Province or State:
MD
Postal Code:
20746
ANNA
MILAN
Role:
DIF AUTHOR
Phone:
(303) 497-5099
Fax:
(303) 497-6513
Email:
ngdc.metadata-support at noaa.gov
Email:
Anna.Milan at noaa.gov
Contact Address:
325 Broadway, Mail Code E/GC4
City:
Boulder
Province or State:
CO
Postal Code:
80305-3328
Country:
USA
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Related URL
Link:
GET DATA
Description:
Download options for Ocean Color Products.
Link:
VIEW EXTENDED METADATA
Description:
View Source Metadata document from the Metadata Manager and Repository (NMMR).
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Creation and Review Dates
DIF Creation Date:
2006-08-29
Last DIF Revision Date:
2008-07-08
Future DIF Review Date:
2007-09-01
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Links
