[cf-satellite] a CF proposal: a convention to provide a general data variable association capability

• To: cf-metadata@xxxxxxxxxxxx, cf-satellite@xxxxxxxxxxxxxxxx
• Subject: [cf-satellite] a CF proposal: a convention to provide a general data variable association capability
• From: Randy Horne <rhorne@xxxxxxxxxxxxxxxxx>
• Date: Fri, 18 May 2012 09:23:22 -0400

Folks:

we have a product type (lightning detections) that has three data variables 
where there is a relationship that must be captured in the NetCDF data set. 

The 3 data variables are (1) flash_energy, (2) group energy), and (3) 
event_energy.

A flash_energy is associated with one or more group_energy elements.  A 
group_energy is associated with one or more event_energy elements.
To support this, have identified 2 new standard attributes,  "association" and 
"associations", and added a concept of an "association variable".

float flash_energy (number_of_flashes);

  :associations = “flash_energy  flash_group_association  group_energy”;

float group_energy (number_of_groups);

  :associations = “flash_energy  flash_group_association group_energy, 
group_energy group_event_association event_energy";

float event_energy (number_of_events);

  :associations = “group_energy  group_event_association  event_energy”;

long flash_group_association (number_of_groups);

  :association = “flash_energy  group_energy”;

long group_event_association (number_of_events);

  :association = “group_energy  event_energy”;

Flash, group, and event association attributes and variables notes

·       There is one association variable to capture the associations between 
individual flashes and groups, and another association variable to capture the 
associations between individual groups and events.

·       The group_energy data variable specifies two associations as it is a 
destination data variable for the flash to group association and a source data 
variable for the group to event association.

·       The extent of the association variables’ dimensions is the same as the 
association’s destination data variable.

*** Note that this convention only makes sense when the affected data variables 
have a single dimension (e.g. points).