Sorry I haven't send what I promise yet -- I've been home sick.
On 12/2/11 1:37 AM, Jonathan Gregory wrote:
> I agree, this is a case for a ragged array, with two unlimited dimensions,
> logically speaking. However such a thing can be accommodated in the new
> discrete geometry conventions
>
> http://www.unidata.ucar.edu/staff/caron/public/CFch9-may10.pdf
>
> This describes two ragged array representations, which are intended for this
> purpose. Only one netCDF unlimited dimension is used; the two logical axes are
> combined into one netCDF axis.
> int row_size(time) ;
> row_size:long_name = "number of particles for this time";
> row_size:sample_dimension = "obs" ;
> double time(obs) ;
> time:standard_name = "time";
> time:units = "days since 1970-01-01 00:00:00" ;
> int particle(obs)
> particle:long_name="particle number";
> float quantity(obs) ;
> quantity:long_name="one of the physical properties of the particle"
> quantity:coordinates = "lat lon alt particle" ;
I'm sorry, I wasn't quite clear -- what you give below is pretty much
what we've arrived at, but I had already considered combining the "two
logical axis" into one unlimited dimension.
The conflict Ute presented what that he doesn't know at the start of the
model run the number of time steps that are required. So he'd like the
time dimension to be unlimited as well -- thus two unlimited dimensions.
The only place the time dimension is used is for the time and row_size
variables, so I can't help thinking there could be a work around. Rich
Signell suggested you could just use a as-big-as-you-might-need time
coordinate -- which is one option.
If I ever feel better -- more later, but I think we are close.
> If there is also
> invariant information for each particle, a large enough particle dimension
> would also be needed and various auxiliary coord vars of this dimension.
That would be a trick if you don't know how many particles you're
starting with -- another nice use for an unlimited dimension...
Thanks,
-Chris
--
Christopher Barker, Ph.D.
Oceanographer
Emergency Response Division
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Chris.Barker at noaa.gov
Received on Fri Dec 02 2011 - 19:10:25 GMT
