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Short Citation:
Office for Coastal Management, 2024: Light Attenuation Kd490,

Item Identification

Title: Light Attenuation Kd490
Status: Completed

This dataset represents monthly and annual mean summaries for Kd490 for the time period from 2000/2001 to 2017/2018, depending on the month and data available (see processing steps). Kd (490) is the diffuse attenuation coefficient at 490 nm. The diffuse attenuation coefficient in water indicates how strongly light intensity at a specified wavelength is attenuated within the water column. This parameter has wide applicability in ocean optics, as it is directly related to the presence of scattering particles in the water column, either organic or inorganic, and thus is an indication of water clarity. The diffuse attenuation coefficient at 490 nm (Kd490) indicates the turbidity of the water column -- how visible light in the blue to green region of the spectrum penetrates within the water column. The value of Kd490 (m-1) represents the rate at which light at 490 nm is attenuated with depth. For example, a Kd490 of 0.1/meter means that light intensity will be reduced one natural log within 10 meters of water. Thus, for a Kd490 of 0.1, one attenuation length is 10 meters. Higher Kd490 value means smaller attenuation depth and lower clarity of ocean water.


To support ocean planning activities pursuant to the Executive Order Regarding the Ocean Policy to Advance the Economic, Security, and Environmental Interests of the United States, the Energy Policy Act, the National Environmental Policy Act, the Rivers and Harbors Act, and the Coastal Zone Management Act.


Theme Keywords

Thesaurus Keyword
ISO 19115 Topic Category
ISO 19115 Topic Category
None coastal
None planning
None renewable energy
None water column
None water quality

Spatial Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Location Keywords
None United States

Physical Location

City: Charleston
State/Province: SC

Data Set Information

Data Set Scope Code: Data Set
Maintenance Frequency: As Needed
Data Presentation Form: Map (digital)
Distribution Liability:

Data Set Credit: ORIGINATORS: NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Ocean Biology Processing Group; Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS), Office for Coastal Management (OCM); Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS);

Support Roles

Point of Contact

CC ID: 1115561
Date Effective From: 2018-06
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202


Currentness Reference: Publication Date

Extent Group 1

Extent Group 1 / Geographic Area 1

CC ID: 1115571
W° Bound: -179.999989
E° Bound: 179.999996
N° Bound: 74.710722
S° Bound: -17.584128

Access Information

Security Class: Unclassified
Data Use Constraints:

For coastal and ocean planning

Distribution Information

Distribution 1

CC ID: 1115562
Download URL:

Distribution 2

CC ID: 1121215
Download URL:

Ocean Reports

Technical Environment


Version 6.2 (Build 9200) ; Esri ArcGIS

Data Quality


The attributes in this dataset are believed to be accurate.

Horizontal Positional Accuracy:

Maximum scale of intended use is 1:80,000.

Completeness Report:

Spatial and attribute properties are believed to be complete, although attribute information has been simplified. Geometric thresholds from original data are preserved. No tests have been completed for exhaustiveness.

Conceptual Consistency:

These data are believed to be logically consistent. Geometry is topologically clean.



Monthly and Annual Summaries for Kd (490)

CC ID: 1115568
Contact Name: NASA Goddard Space Flight Center, Ocean Ecology Laboratory, Ocean Biology Processing Group
Extent Type: Discrete
Extent Start Date/Time: 2018-08-01
Citation URL:
Citation URL Name: Source Online Linkage
Citation URL Description:

URL where the source data were originally accessed.

Source Contribution:

Monthly and Annual Summaries for Kd (490)

Process Steps

Process Step 1

CC ID: 1115569

(1) Downloaded the Level-3 Standard Mapped Image (SMI) for Kd490 data from MODIS for each monthly climatology (summary) and the entire mission composite at 4km resolution.* Additionally all Level-3 SMIs that were used to create the monthly climatology and entire mission composite were downloaded for descriptive statistic calculations. (2) R was used to create Geotiffs of each dataset (GCS WGS 1984). (3) Geotiffs converted to point features – X and Y coordinate field calculated - for the point dataset conversion (not relevant to raster dataset). (4) Point features were clipped by U.S. Economic Exclusion Zone and State waters. (5) All point features were combined into a single feature class. (6) Single point feature class and raster projected into WGS 1984 World Mercator. Temporal resolution for each monthly and annual mean: Kd 490 (m-1) January monthly mean 2001-2018 Kd 490 (m-1) February monthly mean 2000-2018 Kd 490 (m-1) March monthly mean 2000-2018 Kd 490 (m-1) April monthly mean 2000-2018 Kd 490 (m-1) May monthly mean 2000-2018 Kd 490 (m-1) June monthly mean 2000-2017 Kd 490 (m-1) July monthly mean 2000-2017 Kd 490 (m-1) August monthly mean 2000-2017 Kd 490 (m-1) September monthly mean 2000-2017 Kd 490 (m-1) October monthly mean 2000-2017 Kd 490 (m-1) November monthly mean 2000-2017 Kd 490 (m-1) December monthly mean 2000-2017 Kd 490 (m-1) Cumulative mean of entire mission (Annual means 2000-2017 with monthly means from Jan. to May 2018)

Process Date/Time: 2018-08-01 00:00:00

Catalog Details

Catalog Item ID: 66147
GUID: gov.noaa.nmfs.inport:66147
Metadata Record Created By: Brianna Key
Metadata Record Created: 2021-12-22 03:53+0000
Metadata Record Last Modified By: SysAdmin InPortAdmin
Metadata Record Last Modified: 2023-05-30 18:10+0000
Metadata Record Published: 2021-12-22
Owner Org: OCM
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Last Review Date: 2021-12-22
Metadata Review Frequency: 1 Year
Metadata Next Review Date: 2022-12-22