ROM SAF - NRT Notification Detail

NRT Notification Detail

Change of QC procedure for Metop-A and -B GRAS data

DATE: 2014-06-06 15:55
TYPE: NRT-GTS

Description

Dear ROM SAF GTS Users

Issued: 2014-06-06 15:55 UTC

Some time ago (please see original notification below) the ROM SAF
announced an upcoming change in the QC of the level 2a products.
Due to delays it did not happen around August-September last year as
originally announced. The change is now planned for July 1, 2014. We
will provide more details about the exact time when we get closer to
this date.

Please see a description of the implications for the Metop-A and Metop-B
BUFR (and NetCDF) data in the original announcement below. Note that
the change only affects the QC flag and the percent confidence indicator.
There are no changes to the actual data processing at the ROM SAF.

Results of statistical comparisons to ECMWF forecasts, when including
only nominal profiles with the new QC, can be seen in this validation
report: http://www.romsaf.org/product_documents/romsaf_vr_ref_nrt_v14.pdf

If you are interested in access to BUFR test files or other test data we
would be happy to provide this. Please raise such a request through our
helpdesk: http://www.romsaf.org/helpdesk.php

With kind regards
The ROM SAF team

--- Original notification ---

Dear ROM SAF GTS Users

Issued: 2013-07-10 08:37 UTC

At the ROM SAF we are considering some changes to our QC procedure in
the near future. These changes would affect both Metop-A and Metop-B
BUFR (and NetCDF) data.

Our current QC includes the following (among other things that will not
be afftected):
- Retrieved refractivity profiles extending below the ECMWF model
surface are flagged as non-nominal.
- Retrieved refractivity profiles that deviates by more than 10% from
ECMWF forecasts at altitudes below 35 km are flagged as non-nominal.

We plan to change this to:
- Retrieved refractivity profiles that deviates by more than 10% from
ECMWF forecasts at altitudes between 30 and 35 km are flagged as non-nominal.
- Retrieved refractivity profiles that deviates by more than 5% from
ECMWF forecasts at altitudes between 8 and 30 km are flagged as non-nominal.
- The point-by-point 'Percent confidence' indicator for refractivity
(see http://www.romsaf.org/romsaf_bufr.pdf) will be set to 0 (meaning
bad) below 8 km, and 100 (meaning good) above 8 km. This will be done for all
profiles regardless of the QC checks.

Thus there will be no checking for data deviating by more than 10% from
ECMWF forecasts below 8 km, nor will there be a check for whether a
retrieved profile reach below the model surface. Consequently, a number
of profiles that are currently flagged as non-nominal would after this
change be flagged as nominal. But instead the point-by-point 'Percent confidence'
would indicate that the data should not be used below 8 km (for all profiles).

Please let us know if you foresee any problems in your assimilation
system if we were to make these changes. The date for the changes has not yet
been set, but we expect around August-September unless any of our users
(you) will not be able to accommodate the changes.

With kind regards
The ROM SAF team

--- End of original notification ---

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The ROM SAF products are licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0) by EUMETSAT. Whether you're displaying the product as-is or if you have used it as input data, please use the attribution suggested on ROM SAF usage policy and acknowledgement.