Hello,
The histogram records frequencies of a single characteristic of a
variable (in this case for cloud top height). I think that information
about whether or not a cloud exists should not be formally a part of the
histogram. We could adopt the convention for this variable that in the
absence of clouds, the cloud is considered to be "under ground" so the
upper bound of the height of a missing cloud would be 0. [This is
akin to Lorenz's definition of the potential temperature isotherms as
coinciding with the ground in his discussion of available potential energy.]
By the way, I couldn't find this variable in the current release of the
CMIP6 data request. Is it there? If not, could you say a bit more
about how the bins are defined? Are they height or pressure bins?
thanks,
Karl
On 10/11/16 5:41 AM, martin.juckes at stfc.ac.uk wrote:
> Hello,
>
> the CF standard name list has two "histogram_.... " entries, and in the CMIP6 data request we may need to add a third, a histogram_of_cloud_top_height. Besides the standard name, we also need, for this new variable, a method of encoding the "missing data" bin in the histogram. That is, the histogram should record frequency in 16 data bins and one additional bin for the frequency of missing data.
>
> Can we define a "missing_data_index" attribute for histogram variables, and use this to indicate that the first bin in the array has this special purpose. It might be more pythonic to put the _FillValue in the coordinate value for the missing data bin, but I suspect that this would cause substantial problems for many software packages.
>
> regards,
> Martin
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Received on Tue Oct 11 2016 - 11:24:08 BST
