[Go-essp-tech] Fwd: Expected number of variables for which quality control will be needed

[Martina Stockhause]

  Hi, Philip,

I'd like to clarify, what we do in QC checks for level 2:

We calculate global statistical values in order to check them against 
thresholds or if the variation (min/max) of a parameter stays in a 
certain reliable range. More information on the checks is given in the 
document Martin sent around yesterday: CMIP5-AR5-QualityControl-100820.pdf.

The ranges are set currently to ( min_t - ave(min)_t ) > 
magnitude(min_t) * 10^5
ave(min)_t : mean of all minima until the current time step, where 
minimum is the minimum over the whole field. The same ranges are set for 
the maximum.

We are aware that this is quite imprecise, but is able to find runaway 
values.

Best wishes,
Martina



On 01/07/2011 11:22 AM, Bentley, Philip wrote:
> Hi Martin,
>
> It's good to hear that our initial tranche of CMIP5 data 'appears' to
> get the green light. Since we produced the data using the latest (at the
> time) release of CMOR-2 I think, as a project, we'd be in deep doo-doos
> if it hadn't passed :-)
>
> As regards the 4 QC checks you mention below, the first three would
> appear to be fairly cheap operations. However, I'm aware from my own
> recent experience of checking our data outputs that computing the
> min/max bounds for a given atomic dataset (one variable spread over
> numerous netcdf files) is a cpu- and time-expensive operation.
>
> So I was curious to know why this particular check needs to be done?
> Since most of the min/max bounds have been removed from the MIP tables,
> what bounds would be used in the QC L2 checks? Perhaps it's the case
> that this check is simply skipped if no min/max bounds are defined in
> the MIP tables?
>
> Regards,
> Phil
>
>> I hope we can get some conclusion on what constitutes passed
>> QC L2 before the Asheville meeting -- we have some UKMO data
>> which appears to pass all the tests -- but it is hard to be
>> sure because of the complexity of the output from the quality
>> control code. We would like to declare this data as passed,
>> so that we can get onto the next problem (replicating it to
>> other centres).
>>
>> The quality control document (attached) lists 4 objective
>> tests under QC level 2:
>> (1) Number of records in each file consistent with metadata
>> (2) Regular time steps
>> (3) Metadata consistent with data request
>> (4) Minimum and maximum checked against specified ranges (or
>> a default based on the mean).
>>
>> An email from Martina this morning implied that subjective
>> tests would only come in at the QC L3 stage or if there is
>> some doubt about the objective tests.
>>
>> I'm not clear why the process is so complex when the document
>> only specifies a small number of objective tests -- though
>> there clearly is complexity of the workflow (ensuring that
>> results for tests of all files are recorded and retrievable).
>>
>> Regards,
>> Martin
>>
>>
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-- 
----------- DKRZ / Data Management -----------

Martina Stockhause
Deutsches Klimarechenzentrum
Bundesstr. 45a
D-20146 Hamburg
Germany

phone:	+49-40-460094-122
FAX:	+49-40-460094-106
e-mail:	martina.stockhause at zmaw.de

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