ROM SAF - NRT Notification Detail

NRT Notification Detail

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

DATE: 2013-07-10 08:38
TYPE: NRT-GTS

Description

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

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