[mpas-developers] specifying tracers

[Michael Duda]

Mark,

there is actually a capability in the registry to do what you've
described. You'll notice that the last two words in an entry for a
variable in the registry generally are '-' and '-'; these can be
changed to the name of a so-called super-array and a class,
respectively.

Here's a description of how the capability works:

   Two additional columns must now be specified for all variables in the
   Registry file. The first new column specifies the name of the
   'super-array' that a field belongs to in the code (or "-" if the field
   is to be kept as a separate array); the second new column specifies
   the class within the super-array that the field is associated with.
   For example:
   
   var real    qi ( nVertLevels nCells Time ) iro qi scalars moist
   var real    qc ( nVertLevels nCells Time ) iro qc scalars moist
   var real    qr ( nVertLevels nCells Time ) iro qr scalars moist
   var real    o3 ( nVertLevels nCells Time ) iro o3 scalars chem
   var real    no2 ( nVertLevels nCells Time ) iro no2 scalars chem
   
   For each field belonging to a super-array, an index into the
   inner-most dimension of the super-array is automatically defined and
   made available through the grid_types module. This index is named
   xyz_INDEX, where xyz is the name-in-code name specified in the third
   from the last column in the Registry file; this index may then be
   used to access a particular field in its super-array; for example:
   
   scalars(qi_INDEX, k, iCell) = temp_qi
   
   Also, for each class, all fields belonging to that class will be
   located contiguously in the super-array, regardless of their order in
   the Registry file, and they can be accessed collectively through
   automatically-generated indices ccc_start and ccc_end, where ccc is
   the name of the class; for example:
   
   sum_species = sum(scalars(moist_start:moist_end, k, iCell))
   
   Finally, the total number of members of a super-array is defined by an
   automatically-generated variable num_sss, where sss is the name of the
   super-array; for example:
   
   do i=1,num_scalars
      tracer_edge(i) = 0.5*(scalars(i,k,cell1) + scalars(i,k,cell2))
   end do

This description (from the commit for r87) is inaccurate in that
the indices are named index_ccc rather than ccc_index, I think,
but otherwise, it summarizes the capability correctly. We've made
use of this capability in the hydrostatic atmosphere model for
managing tracers; essentially, we now specify 

var real    qv ( nVertLevels nCells Time ) iro qv scalars moist
var real    qc ( nVertLevels nCells Time ) iro qc scalars moist
var real    qr ( nVertLevels nCells Time ) iro qr scalars moist

rather than

var real    tracers ( nTracers nVertLevels nCells Time ) iro tracers - -

in the Registry file src/core_hyd_atmos/Registry to create a
scalars array (we decided to call the array 'scalars' rather than
'tracers') with three members, qv, qc, and qr, which are
accessible as scalars(index_qv,:,:), etc.

Cheers,
Michael


On Mon, Mar 22, 2010 at 01:59:47PM -0600, Mark Petersen wrote:
> Michael,
> 
> I need to assign an index number to temperature and salinity within the 
> tracer array.  Eventually we will have numerous tracers that will need a 
> corresponding tracer index.
> 
> The easiest idea is to have integer variables
> iTemperature=1
> iSalinity=2
> But that requires manual manipulation and reordering as we add tracers.
> 
> A more advanced method is to have an unnumbered list of tracers, perhaps 
> in the Registry, and some function like
>    ind = getTracerIndex('temperature')
> so that the numbering is automatic and hidden.
> 
> Have you given this any thought?  Perhaps mpas already has some indexing 
> capabilities?
> 
> Thanks,
> Mark
> 
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