This message came from the CF Trac system. Do not reply. Instead, enter your comments in the CF Trac system at https://cf-pcmdi.llnl.gov/trac/.
#79: Handling and formatting of vector quantities in CF -----------------------------+---------------------------------------------- Reporter: lavergne | Owner: [email protected] Type: enhancement | Status: reopened Priority: medium | Milestone: Component: cf-conventions | Version: Resolution: | Keywords: vector -----------------------------+---------------------------------------------- Comment (by markh): This ticket has been untouched in 6 months, but it was not clear at this point that there was agreement on the way forward. I am really keen to see this enhancement agreed and implemented, I think it is a particularly useful feature with significant possibilities for CF. I will present my feelings on where this proposal sits, in the hope that this will rekindle the discussion and move it to a resolution. Explicit identification of components and their roles has been stated as important by me and others. An umbrella_name has been suggested in preference to a standard_name, to highlight the difference between the umbrella variable and data or coordinate variables and to keep the standard name table from expanding further (which has to be a good thing). This would suggest that umbrella variables may not have a standard_name attribute. === Proposal === A new variable type is introduced to CF NetCDF: the Umbrella Variable. An umbrella variable may have attributes but it must not have data associated with it and it must not be defined with respect to any NetCDF dimensions. Umbrella variables do not inherit the ability to use any CF data variable attributes. A new attribute: * umbrella_name is introduced, to be used only with umbrella variables. This will be a new controlled vocabulary for CF. A specific type of umbrella variable is defined for the purpose of defining vector quantities. Only spatial vectors are supported. The vector umbrella variable defines a set of attributes for the definition of components: * i_component * j_component * k_component * i_j_direction * k_direction * magnitude Each of these attributes points to one and only one data variable within the dataset. All referenced components are CF data variables which exist in the dataset. Components must be defined on the same domain as each other (all coord definitions must be the same), but the sampling regimes may be different. This is to exclude, for instance, one component variable having time- latitude-longitude and another time-altitude-latitude-longitude as coordinate variables, but it does permit components to be on an Arakawa C-grid. === Example === {{{ int ice_drift_vector; drift_vector:umbrella_name = "sea_ice_displacement_vector" ; drift_vector:long_name = "sea ice drift vector" ; drift_vector:i_component = "dX" ; drift_vector:j_component = "dY" ; drift_vector:i_j_direction = "dir" ; }}} -- Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/79#comment:55> CF Metadata <http://cf-pcmdi.llnl.gov/> CF Metadata This message came from the CF Trac system. To unsubscribe, without unsubscribing to the regular cf-metadata list, send a message to "[email protected]" with "unsubscribe cf-metadata" in the body of your message.
