Data Access Form

Dataset Title:	Chlorophyll-a, Aqua MODIS, NPP, Gulf of Mexico (14 Day Composite)
Institution:	NOAA CoastWatch, West Coast Node (Dataset ID: erdMGchla14day)
Information:	Summary \| License \| FGDC \| ISO 19115 \| Metadata \| Background \| Make a graph

Dimensions	Size	Spacing
time (Centered Time, UTC)	266	13 days 14h 40m 18s (uneven)

altitude (m)	1	(just one value)

latitude (degrees_north)	1201	0.0125 (even)

longitude (degrees_east)	2001	0.0125 (even)

Grid Variables (which always also download all of the dimension variables)
chlorophyll (Concentration Of Chlorophyll In Sea Water, mg m-3)

File type: more info
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(Please be patient. It may take a while to get the data.)

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The Dataset Attribute Structure (.das) for this Dataset

Attributes {
  time {
    String _CoordinateAxisType "Time";
    Float64 actual_range 1.026432e+9, 1.3380768e+9;
    String axis "T";
    Int32 fraction_digits 0;
    String ioos_category "Time";
    String long_name "Centered 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";
    Int32 fraction_digits 0;
    String ioos_category "Location";
    String long_name "Altitude";
    String positive "up";
    String standard_name "altitude";
    String units "m";
  }
  latitude {
    String _CoordinateAxisType "Lat";
    Float64 actual_range 18.0, 33.0;
    String axis "Y";
    String coordsys "geographic";
    Int32 fraction_digits 4;
    String ioos_category "Location";
    String long_name "Latitude";
    String point_spacing "even";
    String standard_name "latitude";
    String units "degrees_north";
  }
  longitude {
    String _CoordinateAxisType "Lon";
    Float64 actual_range -100.0, -75.0;
    String axis "X";
    String coordsys "geographic";
    Int32 fraction_digits 4;
    String ioos_category "Location";
    String long_name "Longitude";
    String point_spacing "even";
    String standard_name "longitude";
    String units "degrees_east";
  }
  chlorophyll {
    Float32 _FillValue -9999999.0;
    Float64 colorBarMaximum 30.0;
    Float64 colorBarMinimum 0.03;
    String colorBarScale "Log";
    String coordsys "geographic";
    Int32 fraction_digits 2;
    String ioos_category "Ocean Color";
    String long_name "Concentration Of Chlorophyll In Sea Water";
    Float32 missing_value -9999999.0;
    String standard_name "concentration_of_chlorophyll_in_sea_water";
    String units "mg m-3";
  }
  NC_GLOBAL {
    String acknowledgement "NOAA NESDIS COASTWATCH, NOAA SWFSC ERD";
    String cdm_data_type "Grid";
    String composite "true";
    String contributor_name "NASA GSFC (OBPG)";
    String contributor_role "Source of level 2 data.";
    String Conventions "COARDS, CF-1.6, Unidata Dataset Discovery v1.0";
    String creator_email "dave.foley@noaa.gov";
    String creator_name "NOAA CoastWatch, West Coast Node";
    String creator_url "http://coastwatch.pfel.noaa.gov";
    String date_created "2012-07-02Z";
    String date_issued "2012-07-02Z";
    Float64 Easternmost_Easting -75.0;
    Float64 geospatial_lat_max 33.0;
    Float64 geospatial_lat_min 18.0;
    Float64 geospatial_lat_resolution 0.0125;
    String geospatial_lat_units "degrees_north";
    Float64 geospatial_lon_max -75.0;
    Float64 geospatial_lon_min -100.0;
    Float64 geospatial_lon_resolution 0.0125;
    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 history 
"NASA GSFC (OBPG)
2012-07-02T01:11:41Z NOAA CoastWatch (West Coast Node) and NOAA SFSC ERD
2013-03-17T23:07:10Z http://oceanwatch.pfeg.noaa.gov/thredds/dodsC/satellite/MG/chla/14day
2013-03-17T23:07:10Z http://coastwatch.pfeg.noaa.gov/erddap/griddap/erdMGchla14day.das";
    String infoUrl "http://coastwatch.pfeg.noaa.gov/infog/MG_chla_las.html";
    String institution "NOAA CoastWatch, West Coast Node";
    String keywords 
"14-day,
Oceans > Ocean Chemistry > Chlorophyll,
aqua, chemistry, chlorophyll, chlorophyll-a, coastwatch, color, composite,
concentration, concentration_of_chlorophyll_in_sea_water, day, degrees, gulf,
mexico, modis, noaa, npp, ocean, ocean color, oceans, sea, seawater, water,
wcn";
    String keywords_vocabulary "GCMD Science Keywords";
    String license 
"The data may be used and redistributed for free but is not intended
for legal use, since it may contain inaccuracies. Neither the data
Contributor, ERD, NOAA, nor the United States Government, nor any
of their employees or contractors, makes any warranty, express or
implied, including warranties of merchantability and fitness for a
particular purpose, or assumes any legal liability for the accuracy,
completeness, or usefulness, of this information.";
    String Metadata_Conventions "COARDS, CF-1.6, Unidata Dataset Discovery v1.0";
    String naming_authority "gov.noaa.pfel.coastwatch";
    Float64 Northernmost_Northing 33.0;
    String origin "NASA GSFC (OBPG)";
    String processing_level "3";
    String project "CoastWatch (http://coastwatch.noaa.gov/)";
    String projection "geographic";
    String projection_type "mapped";
    String references 
"Aqua/MODIS information: http://oceancolor.gsfc.nasa.gov/ . MODIS information:
http://coastwatch.noaa.gov/modis_ocolor_overview.html .";
    String satellite "Aqua";
    String sensor "MODIS";
    String source "satellite observation: Aqua, MODIS";
    String sourceUrl "http://oceanwatch.pfeg.noaa.gov/thredds/dodsC/satellite/MG/chla/14day";
    Float64 Southernmost_Northing 18.0;
    String standard_name_vocabulary "CF-12";
    String summary 
"NOAA CoastWatch distributes chlorophyll-a concentration data from NASA's Aqua
Spacecraft.  Measurements are gathered by the Moderate Resolution Imaging
Spectroradiometer (MODIS) carried aboard the spacecraft.  The algorithm
currently used in processing the water leaving radiance to chlorophyll
concentration has not yet been accepted as science quality.  In addition,
assumptions are made in the atmospheric correction in order to provide the
data in a timely manner.";
    String time_coverage_end "2012-05-27T00:00:00Z";
    String time_coverage_start "2002-07-12T00:00:00Z";
    String title "Chlorophyll-a, Aqua MODIS, NPP, Gulf of Mexico (14 Day Composite)";
    Float64 Westernmost_Easting -100.0;
  }
}

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
http://coastwatch.pfeg.noaa.gov/erddap/griddap/datasetID.fileType{?query}
For example,
http://coastwatch.pfeg.noaa.gov/erddap/griddap/erdBAssta5day.htmlTable?sst[(2007-10-21T00:00:00)][0][(-75):100:(75)][(180):100:(360)]
Thus, the query is often a variable name (e.g., sst),
followed by a set of [] for each of the variable's dimensions
(for example, [time][altitude][latitude][longitude]),
with your desired (start):stride:(stop) values within each [].

For details, see the griddap Documentation.

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