[CF-metadata] Specifying latitude and longitude of transects and regions

From: martin.juckes at stfc.ac.uk <martin.juckes>
Date: Mon, 29 Jun 2015 12:31:37 +0000

Hello All,

There are some variables in the CMIP5 archive which lack explicit latitude and longitude information, such as mfo (standard name sea_water_transport_across_line) and msftzzzba (ocean_y_overturning_mass_streamfunction_due_to_bolus_advection). The first is a mass flux across a transect and the second is a zonally averaged stream function, averaged across an ocean basin.

For transects, the mfo variable is encoded with an index dimension and a coordinate "passage" which labels transects by the name of the passage they cross (e.g. fram_strait). The information about precisely which part of the Fram Strait is used is in a document referred to from the MIP tables. It would be nice to have a means of encoding the end points of the transect in the CF metadata. I looked into using the "bounds" attribute, but that is defined to represent cell boundaries, so an extension to the convention is, I think, needed. It makes sense to follow the pattern used to represent cell boundaries. I propose defining a new attribute "transect" which, like the "bounds" attribute, can be attached to coordinate variables and takes the name of another variable as its value. The named variable should contain the end points of the transect.

The same approach could be used for the streamfunction .. which is a mean across an east-west transect (this approach would lead to a specifcation of the east and west endpoints of each basin at each latitude -- but I'm not sure that it would be feasible to collect that much detail in the CMIP data files).

Is there a cleaner way of encoding transect and basin coordinates?

regards,
Martin
Received on Mon Jun 29 2015 - 06:31:37 BST