[MITgcm-devel] missing-value in meta files

[Martin Losch]

Hi Jean-Michel,
-999 or -999999 is fine with me.

I think I include the misvalIn-array just for completeness. I don't think that we need it now (but one could think of storing data in a packed integer format? Probably not with model output).

Martin

On Jan 11, 2013, at 11:27 PM, Jean-Michel Campin <jmc at ocean.mit.edu> wrote:

> Hi,
> 
> I am going to add the missing-value in the meta file,
> but skipping this additional information if the argument for the missing-value
> is the unlikely missing-value of one (the missing missing-value case).
> 
> But there is a problem when trying to use this missing-value from the
> meta file (ascii) since it could be truncated differently from the value
> in the binary file, and so making things more difficult to use.
> For this reason, I would like to change, in pkg/diagnostics, the default
> missing value to correspond to an integer value; this would reduce
> (hopefully, even eliminate) the risk of different truncations.
> 
> I also think it would make easier/safer the use of missing value even with
> NetCDF output from pkg/diagnostics. The truncation between the
> array value and the stored missing-value is generally not a problem with
> NetCDF files, since both are stored in the same file, using the same
> precision. However, in the (very) special case where I put myself some
> missing value (currently, UNSET_RL) in an _RS array, and fill-up
> a diagnostics with this array to do a snap-shot output, I run into a
> problem of different truncation when _RS is real*4.
> I tested this and rdmnc.m was not able to identify the missing value
> I added in the array.
> 
> The remaining question, assuming we go for changing the default missing value
> in pkg/diagnostics, is which integer value do we pick ?
> I prefer something different from the 123456789 (current UNSET_I),
> to avoid confusion with UNSET_RL/RS.
> I kind of like -999 or -999999 or any of the -9[9 ... 9] family, but it's
> just my preference.
> 
> And just a short question to Martin: do we really need (or will need
> one day) this misvalInt array ? Since all the storage arrays for diagnostics
> are all _RL, not clear to me what it could be used for.
> 
> Cheers,
> Jean-Michel
> 
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