CF parameter meta-data
OpenEarth recommends the use of vocabularies to uniquely identify parameters. We adhere to the vocabularies issued by the Climate Forecast group: CF Metadata. For every parameter add the Attribute standard_name with the associated name in the CF Metadata standard name tables.
A few examples
- all units are to be selected from the Unidata UDUNITS package
- Set a global Attribute to specify which conventions apply to the netCDF file.
- The CF convenctions require that all parameters should have an attribute "standard_name" that is selected from the CF standard_names
- All variabels should have the following attributes:
- units
- standard_name
- actual_range = (min max) or valid_range=(min max): recommended to facilitate generation of catalogs.
- Examples for some frequently used parameters:
- time is stored according to the CF convenction as 'days since 1970-1-1 00:00:00 +00:00' (this is the linux epoch). To avoid confusion due to different calenders in the first two milennia AD, we recommend to select the reference data in the 20th century (instead of for instance at the imaginary date 0000-0-0 as matlab does). To prevent loss of precision for high-frequency data we recommend to store all dates as doubles when necesarry. Please do include the timezone for high-frequency data.
- units= 'days since 1970-1-1 00:00:00 +00:00'
- standard_name = 'time'
- longitude coordinate
- standard_name = 'longitude'
- units= 'degrees_east'
- latitude coordinate
- standard_name = 'latitude'
- units= 'degrees_north'
- wind direction
- standard_name = 'wind_from_direction' or 'wind_to_direction'
- units= 'degree_true' when using the nautical convenction.
- time is stored according to the CF convenction as 'days since 1970-1-1 00:00:00 +00:00' (this is the linux epoch). To avoid confusion due to different calenders in the first two milennia AD, we recommend to select the reference data in the 20th century (instead of for instance at the imaginary date 0000-0-0 as matlab does). To prevent loss of precision for high-frequency data we recommend to store all dates as doubles when necesarry. Please do include the timezone for high-frequency data.
- How to store grid data is precisely described on the CF Metadata pages.
- Point Observation Data are also defined in the CF Metadata are defined:
- point: one or more parameters measured at one point in time and space
- stationTimeSeries: a time-series of data points at the same location, with varying time
- trajectory: a connected set of data points along a 1D curve in time and space
- profile: a set of data points along a vertical line
- stationProfileTimeSeries: a time-series of profiles at a named location
- section: a collection of profiles which originate along a trajectory.
