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A first check to determine whether a given NetCDF file can be imported in FEWS is to use an online CF compliance checker, see e.g. http://cfconventions.org/compliance-checker.html or https://compliance.ioos.us/index.html. If the NetCDF file is not valid according to the CF compliance checker, then the NetCDF file can probably not be imported in FEWS. In this case please contact the data supplier that created the NetCDF file and ask them to make the NetCDF file CF-1.6 compliant. If the file is not CF-1.6 compliant then there is no reason to contact the FEWS support team.

Scalar Time Series Example

Netcdf file: scalar_time_series.nc

Text version: scalar_time_series.txt

Regular Grid Time Series Example

Netcdf file:  regular_grid_time_series.nc

Text version: regular_grid_time_series.txt

Curvilinear Grid Time Series Example

Also note that there can be slight differences between importing a grid from a netCDF file into Delft-FEWS and into other viewers. For example a netCDF file with a rotated pole grid that contains both one-dimensional coordinate variables in the rotated coordinate system and two-dimensional coordinate variables in the WGS1984 system. Panoply will read from this file the two-dimensional coordinate variables. Delft-FEWS can read from this file either the two-dimensional coordinate variables (irregular grid definition) or the one-dimensional coordinate variables (regular grid definition, i.e. more efficient, better performance). If the one-dimensional coordinate variables or grid mapping in this netCDF file are not CF compliant, then this might result in problems in Delft-FEWS, which are not visible in Panoply.

Scalar Time Series Example

Netcdf file: scalarNetcdf file: curvilinear_grid_time_series.nc

Text version: curvilinear_gridscalar_time_series.txt

Unstructured Regular Grid (UGRID) Time Series

For an example of data in UGRID format, see http://ugrid-conventions.github.io/ugrid-conventions/

Example

Netcdf file:  regular_grid_time_series.nc

Text version: regular_grid_time_series.txt

Curvilinear Grid Time Series Example

Netcdf file: curvilinear_grid_time_series.nc

Text version: curvilinear_grid_time_series.txt

Unstructured Grid (UGRID) Time Series

For an example of data in UGRID format, see http://ugrid-conventions.github.io/ugrid-conventions/

To import unstructured grid To import unstructured grid data in Delft-FEWS you need to add an irregular grid definition to the grids.xml configuration file for your data. For more information see 06 Grids.Grids#06Grids-UsingaUGRIDNetCDFfileasunstructuredgriddefinition

Track Time Series (single trajectory per file)

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The global attribute "Conventions" must be specified in the netcdf file (e.g. Conventions="CF-1.6"). If this attribute is not present or not valid, then the NetCDF Java library assumes a default convention (different from CF), which can cause unexpected behaviour in the NetCDF import in Delft-FEWS. Also see http://cfconventions.org/Data/cf-conventions/cf-conventions-1.6/build/cf-conventions.html#identification-of-conventions.

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Gridded data

See for references to the cf-conventions website below.

1. all variables (data and coordinate variables ) must have a unique variable name and the following attributes:
   1. units (required, see units link below)
   2. standard_name (required, see standard_name link below) - should comply with standard names list
   3. long_name (recommended, see long_name links below)
   4. _FillValue and/or missing_value (required if
   there are
   1. data contains missing values
   in the data
   1. )
   2. scale_factor (optional to compact data)
   3. add_offset (optional to compact data)
   Also see http://cfconventions.org/Data/cf-conventions/cf-conventions-1.6/build/cf-conventions.html#units, http://cfconventions.org/Data/cf-conventions/cf-conventions-1.6/build/cf-conventions.html#long-name and http://cfconventions.org/Data/cf-conventions/cf-conventions-1.6/build/cf-conventions.html#standard-name.
2. the standard_name attributes should comply to the list with standard names, see http://cfconventions.org/26.html.
a data variable for a 2D grid must depend on three dimensions, representing time and two spatial dimensions (in the order time, y, x). The names of the dimensions can be anything. For the time dimension there must be a corresponding 1D time coordinate variable with the same name. If the grid is regular or rectangular, then for each spatial dimension there must be a corresponding 1D coordinate variable with the same name. See http://cfconventions.org/Data/cf-conventions/cf-conventions-1.6/build/cf-conventions.html#idp5553648. If the grid is curvilinear, then the y and x coordinate variables are both 2D and depend on both spatial dimensions. In this case the data variable must have an attribute "coordinates" that refers to the y and x coordinate variables (in that order), e.g. coordinates="y x". See
3. Data variable for a 2D grid must depend on three dimensions, representing time and two spatial dimensions (in either the order time, y, x or time, x, y).  The names of the dimensions can be anything.
   1. Time dimension must have a corresponding 1D time coordinate variable with the same name.
   2. Spatial dimensions, for
      1. regular or rectangular grids - each spatial dimension must have a corresponding 1D coordinate variable with the same name (see coordinates link below).
      2. curvilinear grids -  both spatial dimensions are 2D and depend on both spatial dimensions.
         1. The data variable must have an attribute "coordinates" that refers to the y and x coordinate variables (in that order), e.g. coordinates="y x"
         2. Each coordinate variable must have an attribute "axis" that indicates which axis is defined by that coordinate variable.
            1. Time coordinate variable requires axis "T"
            2. x coordinate variable requires axis "X"
            3. y coordinate variable requires axis "Y"
            4. (optional) analysis_time coordinate, see below
4. Time coordinate variable must have the attributes
   1. "units" with a valid unit of time - e.g. units="minutes since 1970-01-01 00:00:00.0 +0000" (time coordinate link below)
   2. "axis" with value "T"
5. Time and spatial coordinate variables must have values either in ascending or in descending order.
6. Forecast reference time/analysis time/base time (optional), must be stored in a separate coordinate variable that
   1. contains only one value: the forecast reference time, and
   2. standard_name="forecast_reference_time"

The name of this variable must be present in the coordinates attribute of the data variable, e.g. coordinates="analysis_time" or coordinates="y x analysis_time".
If needed, different data variables can point to different forecast reference time variables (see scalar coordinate link below).

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Compacted data

Netcf data variables with attributes scale_factor and add_offset will be treated as compacted data and the values of these attributes will be used to uncompact the values of this variable.

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