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Extract Mesoscale Eddy Tracklines From SpatiaLite Database

Extracts eddy tracklines from the Chelton et al. (2011) mesoscale eddy database in SpatiaLite format.

In order to use this tool, you must first download the mesoscale eddy database netCDF file (usually available at http://cioss.coas.oregonstate.edu/eddies/) and convert it to a SpatiaLite database using the Convert Mesoscale Eddies NetCDF to SpatiaLite Database tool.

Each line represents the track of an eddy and includes attributes such as the start date, end date, duration, polarity, and various summary statistics. The track is constructed by connecting the eddy centroid points present in the database.

Because the database includes over 200,000 eddies, we recommend that you use the Where Clause parameter to limit the extraction to the eddies that occured in your region and time period of interest. If you do not specify the Where Clause, all 200,000 tracks will be extracted, which may take 30-45 minutes on a relatively fast computer and produce an output feature class that requires 50-100 MB of disk space.

References

Chelton, D.B., M.G. Schlax, and R.M. Samelson (2011). Global observations of nonlinear mesoscale eddies. Progress in Oceanography 91: 167-216.


Command line syntax

CheltonMesocaleEddyPointsExtractArcGISLinesFromSpatiaLite_GeoEco <spatiaLiteDB> <outputFeatureClass> {tableName} {where}

Parameters
ExpressionExplanation
<spatiaLiteDB>

Mesoscale eddies SpatiaLite database to read.

This database is produced from the mesoscale eddy database netCDF file (usually available at http://cioss.coas.oregonstate.edu/eddies/) by the Convert Mesoscale Eddies NetCDF to SpatiaLite Database tool.

<outputFeatureClass>

Line feature class to create.

Each line represents an eddy track. Longitude coordinates will range from 0 to 360. Tracks that cross the Prime Meridian will be split into multi-part lines.

The lines will have the following attributes; data types are indicated in parentheses following the field name.

  • track (integer) - eddy identification number.

  • duration (integer) - duration of the eddy, in weeks.

  • startdate (date) - date the eddy was first observed.

  • enddate (date) - date the eddy was last observed.

  • cyc (integer) - polarity of the eddy: -1 for cyclonic eddies and +1 for anticyclonic eddies.

  • minA, maxA, meanA (float) - minimum, maximum, and mean per-centroid eddy amplitude (cm), defined to be the magnitude of the height difference between the extremum of SSH within the eddy and the SSH around the contour defining the perimeter of the eddy. These statistics are calculated from the A parameter of the eddy centroids that make up the track.

  • minL, maxL, meanL (float) - minimum, maximum, and mean per-centroid eddy radius scale (km), defined to be the radius of a circle with area equal to that enclosed by the contour of SSH within the eddy around which the circum-average speed is maximum. These statistics are calculated from the L parameter of the eddy centroids that make up the track.

  • minU, maxU, meanU (float) - minimum, maximum, and mean per-centroid average speed (cm/sec) around the SSH contour that defines the scale L, i.e., the maximum circum-average speed within the eddy. These statistics are calculated from the U parameter of the eddy centroids that make up the track.

Please see Chelton et al. (2011) and http://cioss.coas.oregonstate.edu/eddies/ for more information about how these parameters were calculated.

A spatial index will be created on the output feature class.

{tableName}

Name of the table to read from the SpatiaLite database.

{where}

SQL WHERE clause expression that specifies the eddy centroids that identify the eddy tracks to extract. If this parameter is not provided, all of the tracks will be extracted.

The expression should reference the attributes of the centroids, not the tracks. Please see the documentation for the Convert Mesoscale Eddies NetCDF to SpatiaLite Database tool for a description of the centroid attributes.

If this expression does not select all of the centroids that make up a track, the entire track will be extracted anyway. For example, if the expression specifies a geographic bounding box, complete tracks will be extracted for all eddies that had at least one centroid occur within the box.

The expression is evaluated by the SQLite database engine that SpatiaLite is built upon. Please see the SQLite documentation for more information about the syntax of this expression.

The following expression shows how to specify a geographic bounding box and time window to extract tracks that had at least one centroid occur in a region of the north Atlantic in the first three months of 2000. Note that longitude ranges from 0 to 360:

lat >= 25 and lat <= 50 and lon >= 280 and lon <= 340 and obsdate >= '2000-01-01' and obsdate <= '2000-03-31'

This example shows how to extract the tracks that had at least one centroid in the southern hemisphere, that had a duration of at least 16 weeks, and that had anticyclonic polarity:

lat < 0 and n >= 17 and cyc = 1

You may use SpatiaLite's SQL functions in this expression to perform spatial comparisons. Please see the SpatiaLite documentation for more information.

Scripting syntax

CheltonMesocaleEddyPointsExtractArcGISLinesFromSpatiaLite_GeoEco (spatiaLiteDB, outputFeatureClass, tableName, where)

Parameters
ExpressionExplanation
Mesoscale eddies SpatiaLite database (Required)

Mesoscale eddies SpatiaLite database to read.

This database is produced from the mesoscale eddy database netCDF file (usually available at http://cioss.coas.oregonstate.edu/eddies/) by the Convert Mesoscale Eddies NetCDF to SpatiaLite Database tool.

Output feature class (Required)

Line feature class to create.

Each line represents an eddy track. Longitude coordinates will range from 0 to 360. Tracks that cross the Prime Meridian will be split into multi-part lines.

The lines will have the following attributes; data types are indicated in parentheses following the field name.

  • track (integer) - eddy identification number.

  • duration (integer) - duration of the eddy, in weeks.

  • startdate (date) - date the eddy was first observed.

  • enddate (date) - date the eddy was last observed.

  • cyc (integer) - polarity of the eddy: -1 for cyclonic eddies and +1 for anticyclonic eddies.

  • minA, maxA, meanA (float) - minimum, maximum, and mean per-centroid eddy amplitude (cm), defined to be the magnitude of the height difference between the extremum of SSH within the eddy and the SSH around the contour defining the perimeter of the eddy. These statistics are calculated from the A parameter of the eddy centroids that make up the track.

  • minL, maxL, meanL (float) - minimum, maximum, and mean per-centroid eddy radius scale (km), defined to be the radius of a circle with area equal to that enclosed by the contour of SSH within the eddy around which the circum-average speed is maximum. These statistics are calculated from the L parameter of the eddy centroids that make up the track.

  • minU, maxU, meanU (float) - minimum, maximum, and mean per-centroid average speed (cm/sec) around the SSH contour that defines the scale L, i.e., the maximum circum-average speed within the eddy. These statistics are calculated from the U parameter of the eddy centroids that make up the track.

Please see Chelton et al. (2011) and http://cioss.coas.oregonstate.edu/eddies/ for more information about how these parameters were calculated.

A spatial index will be created on the output feature class.

SpatiaLite table name (Optional)

Name of the table to read from the SpatiaLite database.

Where clause (Optional)

SQL WHERE clause expression that specifies the eddy centroids that identify the eddy tracks to extract. If this parameter is not provided, all of the tracks will be extracted.

The expression should reference the attributes of the centroids, not the tracks. Please see the documentation for the Convert Mesoscale Eddies NetCDF to SpatiaLite Database tool for a description of the centroid attributes.

If this expression does not select all of the centroids that make up a track, the entire track will be extracted anyway. For example, if the expression specifies a geographic bounding box, complete tracks will be extracted for all eddies that had at least one centroid occur within the box.

The expression is evaluated by the SQLite database engine that SpatiaLite is built upon. Please see the SQLite documentation for more information about the syntax of this expression.

The following expression shows how to specify a geographic bounding box and time window to extract tracks that had at least one centroid occur in a region of the north Atlantic in the first three months of 2000. Note that longitude ranges from 0 to 360:

lat >= 25 and lat <= 50 and lon >= 280 and lon <= 340 and obsdate >= '2000-01-01' and obsdate <= '2000-03-31'

This example shows how to extract the tracks that had at least one centroid in the southern hemisphere, that had a duration of at least 16 weeks, and that had anticyclonic polarity:

lat < 0 and n >= 17 and cyc = 1

You may use SpatiaLite's SQL functions in this expression to perform spatial comparisons. Please see the SpatiaLite documentation for more information.