[CF-metadata] Conventions for use of local solar time in gridded climate data

From: Mitchelson, Joel <joel.mitchelson>
Date: Thu, 28 Jul 2016 11:58:49 +0000

Dear cf-metadata community,

We are working on new high resolution daily data sets of climate observations as part of the EUSTACE project ( http://www.eustaceproject.eu/ ), where fields such as surface air temperature are presented on global grids, and the sampling period for each grid box is from midnight to midnight in local solar time. In other words, the UTC time period of each grid box depends on longitude.

It seems that within CF conventions there might be several possible approaches to expressing this, though no specific example appears to be given in the conventions documents (versions 1.6 or 1.7). It would be desirable if our chosen method works nicely with as many existing software tools as possible; and uses established conventions if they exist.

Do conventions for this already exist?

If not, is the example CDL fragment below likely to be easy to use within many existing software tools for working with gridded fields of climate data, or might there be a more widely compatible method?

Many thanks in advance for your kind attention.

Joel.

--
Dr. Joel R. Mitchelson  Observational Climate Data Software Specialist
Met Office Hadley Centre  FitzRoy Road  Exeter  Devon  EX1 3PB  United Kingdom
--
// Example CDL fragment representing a single day of data in one NetCDF file.
// To represent more than one day multiple files could be used, 
// or else a single file with the localtime dimension set to equal the number of days.
dimensions:
    localtime = UNLIMITED ; // (1 currently)
    latitude = 720 ;
    longitude = 1440 ;
    bounds = 2 ;
variables:
    float time(localtime, longitude) ;
        time:units = "days since 1850-1-1 0:0:0" ;
        time:long_name = "Time (days)" ;
        time:standard_name = "time" ;
        time:bounds = "timebounds" ;
        time:calendar = "gregorian" ;
    float timebounds(localtime, longitude, bounds)
    float latitude(latitude) ;
        latitude:units = "degrees_north" ;
        latitude:long_name = "Latitude (deg)" ;
        latitude:standard_name = "latitude" ;
    float longitude(longitude) ;
        longitude:units = "degrees_east" ;
        longitude:long_name = "Longitude (deg)" ;
        longitude:standard_name = "longitude" ;
    short tas(localtime, latitude, longitude) ;
        tas:units = "K" ;
        tas:long_name = "Mean daily surface air temperature (K)" ;
        tas:standard_name = "air_temperature" ;
        tas:coordinates = "time" ;
        tas:cell_methods = "time: mean" ;
        tas:_FillValue = -32768s ;
        tas:scale_factor = 0.002 ;
        tas:add_offset = 273.15 ;

Received on Thu Jul 28 2016 - 05:58:49 BST