ERDDAP > griddap > Data Access Form

Dataset Title:	Chlorophyll-a Anomaly (difference), NOAA-20 VIIRS, Science Quality, 2km Global WW00, Daily
Institution:	NOAA NESDIS STAR   (Dataset ID: noaacwN20VIIRSSCIchlanomdifDaily)
Information:	Summary | License | FGDC | ISO 19115 | Metadata | Background | Files | Make a graph

 

Dimensions	Start	Stride	Stop	Size	Spacing
time (UTC)				2672	1 day 0h 18m 20s (uneven)
altitude (m)				1	(just one value)
latitude (degrees_north)				8619	-0.02083188 (uneven)
longitude (degrees_east)				17282	0.02083092 (uneven)

Grid Variables (which always also download all of the dimension variables)

chlor_a_diff (Chlorophyll_a anomaly, daily minus 61 day composite, mg m^-3)

File type: (more information) .asc - View OPeNDAP-style ISO-8859-1 comma-separated text. .croissant - Download the dataset croissant schema. .csv - Download a ISO-8859-1 comma-separated text table (line 1: names; line 2: units; ISO 8601 times). .csv0 - Download a ISO-8859-1 .csv file without column names or units. Times are ISO 8601 strings. .csvp - Download a ISO-8859-1 .csv file with line 1: name (units). Times are ISO 8601 strings. .das - View the dataset's metadata via an ISO-8859-1 OPeNDAP Dataset Attribute Structure (DAS). .dds - View the dataset's structure via an ISO-8859-1 OPeNDAP Dataset Descriptor Structure (DDS). .dods - OPeNDAP clients use this to download the data in the DODS binary format. .esriAscii - Download an ISO-8859-1 ESRI ASCII file (latitude longitude data only; longitude must be all below or all above 180). .fgdc - View the dataset's UTF-8 FGDC .xml metadata. .htmlTable - View a UTF-8 .html web page with the data in a table. Times are ISO 8601 strings. .iso19115 - View the dataset's ISO 19115/19139 UTF-8 .xml metadata using the version default for this server. .iso19115_2 - View the dataset's ISO 19115-2/19139 UTF-8 .xml metadata. .iso19115_3_2016 - View the dataset's ISO 19115-3:2016 UTF-8 .xml metadata. .iso19139_2007 - View the dataset's ISO 19139:2007 UTF-8 .xml metadata. .itx - Download an ISO-8859-1 Igor Text File. Each axis variable and each data variable becomes a wave. .json - View a table-like UTF-8 JSON file (missing value = 'null'; times are ISO 8601 strings). .jsonlCSV - View a UTF-8 JSON Lines CSV file without column names (mv = 'null'; times are ISO 8601 strings). .jsonlCSV1 - View a UTF-8 JSON Lines CSV file with column names on line 1 (mv = 'null'; times are ISO 8601 strings). .jsonlKVP - View a UTF-8 JSON Lines file with Key:Value pairs (missing value = 'null'; times are ISO 8601 strings). .mat - Download a MATLAB binary file. .nc - Download a NetCDF-3 binary file with COARDS/CF/ACDD metadata. .ncHeader - View the UTF-8 header (the metadata) for the NetCDF-3 .nc file. .nccsv - Download a NetCDF-3-like 7-bit ASCII NCCSV .csv file with COARDS/CF/ACDD metadata. .nccsvMetadata - View the dataset's metadata as the top half of a 7-bit ASCII NCCSV .csv file. .ncml - View the dataset's structure and metadata as a UTF-8 NCML .xml file. .ncoJson - Download a UTF-8 NCO lvl=2 JSON file with COARDS/CF/ACDD metadata. .odvTxt - Download time,latitude,longitude,otherVariables as an ODV Generic Spreadsheet File (.txt). .parquet - Download as a parquet file. Metadata contains column names ("column_names") and units ("column_units"). .parquetWMeta - Download as a parquet file with detailed metadata. .timeGaps - View a UTF-8 list of gaps in the time values which are larger than the median gap. .tsv - Download a ISO-8859-1 tab-separated text table (line 1: names; line 2: units; ISO 8601 times). .tsv0 - Download a ISO-8859-1 .tsv file without column names or units. Times are ISO 8601 strings. .tsvp - Download a ISO-8859-1 .tsv file with line 1: name (units). Times are ISO 8601 strings. .wav - Download a .wav audio file. All columns must be numeric and of the same type. .xhtml - View a UTF-8 XHTML (XML) file with the data in a table. Times are ISO 8601 strings. .geotif - View a grayscale GeoTIFF .tif file (for latitude longitude data; longitude must be all below or all above 180). .kml - View a Google Earth .kml file (for latitude, longitude data only). .largePdf - View a large .pdf image file with a graph or map. .largePng - View a large .png image file with a graph or map. .pdf - View a standard, medium-sized .pdf image file with a graph or map. .png - View a standard, medium-sized .png image file with a graph or map. .smallPdf - View a small .pdf image file with a graph or map. .smallPng - View a small .png image file with a graph or map. .transparentPng - View a .png image file (just the data, without axes, landmask, or legend).

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The Dataset Attribute Structure (.das) for this Dataset

Attributes {
  time {
    String _CoordinateAxisType "Time";
    Float64 actual_range 1.5324336e+9, 1.7661456e+9;
    String axis "T";
    String calendar "gregorian";
    String ioos_category "Time";
    String long_name "Time";
    String standard_name "time";
    String time_origin "01-JAN-1970 00:00:00";
    String units "seconds since 1970-01-01T00:00:00Z";
  }
  altitude {
    String _CoordinateAxisType "Height";
    String _CoordinateZisPositive "up";
    Float64 actual_range 0.0, 0.0;
    String axis "Z";
    String ioos_category "Location";
    String long_name "Altitude";
    String positive "up";
    String standard_name "altitude";
    String units "m";
  }
  latitude {
    String _CoordinateAxisType "Lat";
    Float32 actual_range -89.76459, 89.76459;
    String axis "Y";
    String ioos_category "Location";
    String long_name "Latitude";
    String standard_name "latitude";
    String units "degrees_north";
    Float32 valid_max 90.0;
    Float32 valid_min -90.0;
  }
  longitude {
    String _CoordinateAxisType "Lon";
    Float32 actual_range -179.9896, 179.9896;
    String axis "X";
    String ioos_category "Location";
    String long_name "Longitude";
    String standard_name "longitude";
    String units "degrees_east";
    Float32 valid_max 180.0;
    Float32 valid_min -180.0;
  }
  chlor_a_diff {
    Float32 _FillValue -999.0;
    String C_format "%.4g";
    String cell_methods "time:mean";
    Float64 colorBarMaximum 10.0;
    Float64 colorBarMinimum -10.0;
    String coverage_content_type "physicalMeasurement";
    String ioos_category "Ocean Color";
    String long_name "Chlorophyll_a anomaly, daily minus 61 day composite";
    String standard_name "chlorophyll_a_anomaly";
    String units "mg m^-3";
    Float32 valid_max 20.0;
    Float32 valid_min -20.0;
  }
  NC_GLOBAL {
    String _lastModified "2025-12-28T19:25:06.000Z";
    String cdm_data_type "Grid";
    String Conventions "CF-1.6 ACDD-1.3, COARDS";
    String creator_email "coastwatch.info@noaa.gov";
    String creator_name "NOAA CoastWatch";
    String creator_type "institution";
    String creator_url "https://coastwatch.noaa.gov";
    String date_created "2025-12-28T19:25:06.000Z";
    Float64 Easternmost_Easting 179.9896;
    Float64 geospatial_lat_max 89.76459;
    Float64 geospatial_lat_min -89.76459;
    String geospatial_lat_units "degrees_north";
    Float64 geospatial_lon_max 179.9896;
    Float64 geospatial_lon_min -179.9896;
    String geospatial_lon_units "degrees_east";
    Float64 geospatial_vertical_max 0.0;
    Float64 geospatial_vertical_min 0.0;
    String geospatial_vertical_positive "up";
    String geospatial_vertical_units "m";
    String grid_mapping_epsg_code "EPSG:4326";
    Float32 grid_mapping_inverse_flattening 298.2572;
    Float32 grid_mapping_longitude_of_prime_meridian 0.0;
    String grid_mapping_name "latitude_longitude";
    String grid_mapping_proj4_params "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs";
    Float32 grid_mapping_semi_major_axis 6378137.0;
    String history 
"/data/data369/hgu/v224/bin/l3mapgen par=/data/data652/coastwatch/oc/L3/scripts/bin/../config/l3mapgen_par_chlor_a_diff ifile=/data/data652/coastwatch/oc/L3/scripts/bin/../temp/Config_n20_chlor_a_diff/infile_2km_G.nc ofile=/data/data369/viirs/L3map/2025/12/19/V2025353_D1_N20_SCI_WW00_chlor_a_diff.nc   Sun Dec 28 19:25:18 2025
: /data/data652/coastwatch/oc/L3/scripts/bin/l3cnvtr -s NOAA-20 /data/data369/viirs/L3map/2025/12/19/V2025353_D1_N20_SCI_WW00_chlor_a_diff.nc /data/aftp/socd1/mecb/coastwatch/viirs/science/L3/global/chlora/anom_n20/WW00/2025/V2025353_D1_N20_SCI_WW00_chloradiff.nc
2025-12-29T22:49:55Z (local files)
2025-12-29T22:49:55Z https://coastwatch.noaa.gov/erddap/griddap/noaacwN20VIIRSSCIchlanomdifDaily.das";
    String id "L3//data/data650/L3bin_global/VIIRSJ1/noaa_msl12_bmw/61day/2025/20250515/2km/infile_2km_G.nc";
    String identifier_product_doi "https://dx.doi.org";
    String identifier_product_doi_authority "https://dx.doi.org";
    String infoUrl "https://coastwatch.noaa.gov";
    String institution "NOAA NESDIS STAR";
    String instrument "VIIRS";
    String keywords "altitude, anomaly, chlor_a_diff, chlorophyll, chlorophyll_a_anomaly, color, composite, cylindrical, daily, data, day, enviro                                                                               nmental, equidistant, image, imager, imager/radiometer, imaging, information, infrared, level, level-3, mapped, minus, national, nesdis, noaa, npp, ocean, ocean color, orbiting, partnership, polar, polar-orbiting, radiometer, satellite, service, star, suite, suite/suomi-npp, suomi, time, v                                                                               iirsn, viirs, viirs-n, visible";
    String keywords_vocabulary "NASA Global Change Master Directory (GCMD) Science Keywords";
    String l2_flag_names "ATMFAIL,LAND,HIGLINT,HILT,HISATZEN,CLOUD,HISOLZEN,LOWLW,CHLFAIL,NAVWARN,CLDSHDSTL,MAXAERITER,CHLWARN,ALGICE,SEAICE,NAVFAIL,FILTER";
    String license "These data may be redistributed and used without restriction.";
    String map_projection "geographic";
    String measure "Mean";
    String Metadata_Conventions "Unidata Dataset Discovery v1.0";
    String naming_authority "gov.noaa.coastwatch";
    Float64 Northernmost_Northing 89.76459;
    String platform "NOAA-20";
    String processing_level "L3 Mapped";
    String product_name "V2025353_D1_N20_SCI_WW00_chloradiff.nc";
    String project "Ocean Color Science Team (NOAA/NESDIS/STAR/OCST)";
    String publisher_email "coastwatch.info@noaa.gov;ncei.info@noaa.gov";
    String publisher_name "NOAA CoastWatch;National Centers for Environmental Information (NCEI)";
    String publisher_type "group";
    String publisher_url "https://coastwatch.noaa.gov;https://www.ncei.noaa.gov/";
    String Satellite "NOAA-20";
    String Sensor "VIIRS";
    String sourceUrl "(local files)";
    Float64 Southernmost_Northing -89.76459;
    String spatialResolution "2.32 km";
    String standard_name_vocabulary "NetCDF Climate and Forecast (CF) Metadata Convention";
    String summary "Visible and Infrared Imager/Radiometer Suite/Suomi-NPP (VIIRSN) Level-3 Equidistant Cylindrical Mapped Image";
    String temporal_range "day";
    String testOutOfDate "now-7days";
    String time_coverage_end "2025-12-19T12:00:00Z";
    String time_coverage_start "2018-07-24T12:00:00Z";
    String title "Chlorophyll-a Anomaly (difference), NOAA-20 VIIRS, Science Quality, 2km Global WW00, Daily";
    Float64 Westernmost_Easting -179.9896;
  }
}

 

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Using griddap to Request Data and Graphs from Gridded Datasets

griddap lets you request a data subset, graph, or map from a gridded dataset (for example, sea surface temperature data from a satellite), via a specially formed URL. griddap uses the OPeNDAP Data Access Protocol (DAP) and its projection constraints.

The URL specifies what you want: the dataset, a description of the graph or the subset of the data, and the file type for the response.

• (easy) You can get data by using the dataset's Data Access Form. It makes the URL for you.
• (easy) You can make a graph or map by using the dataset's Make A Graph form. It makes the URL for you.
• (not hard) You can bypass the forms and get the data or make a graph or map by generating the URL by hand or with a computer program or script.

griddap request URLs must be in the form
https://coastwatch.pfeg.noaa.gov/erddap/griddap/datasetID.fileType{?query}
For example,
https://coastwatch.pfeg.noaa.gov/erddap/griddap/jplMURSST41.htmlTable?analysed_sst[(2002-06-01T09:00:00Z)][(-89.99):1000:(89.99)][(-179.99):1000:(180.0)]
Thus, the query is often a data variable name (e.g., analysed_sst), followed by [(start):stride:(stop)] (or a shorter variation of that) for each of the variable's dimensions (for example, [time][latitude][longitude]).

For details, see the griddap Documentation.