The main purpose of the monthly IFS blacklist information sent out via e-mail is to provide guidance for data assimilation purposes.
If a station appears in the IFS blacklist it does not necessarily suggest poor observation quality. Stations may be blacklisted because of limited representativeness relative to the IFS grid scale, or it may be a new station which is being passively monitored for a certain period before being actively used by the IFS data assimilation. Some temporary blacklisting may be associated with the TAC->BUFR transition.
If a station appears in the IFS blacklist this does not necessarily suggest poor observation quality.
New stations may be passively monitored for a certain period before being actively used by the IFS data assimilation.
ECMWF may not use an observation because (for example) it is in a fjord not resolved by
the ECMWF model, whereas this would be usable in a higher resolution model.
There are also some complications due to the TAC to BUFR migration, see the
overview at https://confluence.ecmwf.int/display/TCBUF/ .
The blacklist code shared in the monthly e-mails is tailored to the IFS and needs to be used with caution in other NWP systems, especially those with higher spatial resolution.
For further questions on potential station quality issues please refer to the EUMETNET/EUCOS portal: https://portal.eumetnet.eu
ECMWF aims to implement IFS blacklist changes in the second week of each month. During the first week, analysts evaluate automated and manual proposals for changes and run model experiments to test the blacklist change. Operational change requests are then submitted in the second week of the month (typically Monday or Tuesday). Occasionally operational IT constraints mean the change is postponed by a few days.
The blacklist changes include preparations for TAC to BUFR migrations. This is clearly indicated in the change document, i.e. denoted by subtype of the observations in the whitelist sections.
Every three months there is a synchronisation with WMO's OSCAR station database. This generally warrants a short blacklist change proposal of its own. The change is integrated into the blacklist code and the relevant change document can be passed on as well.
If you would like to be added to the e-mail distribution of this blacklist information please send an email to ifs_conventional_blacklist-request@lists.ecmwf.int with the word subscribe or unsubscribe as Subject. Please note that this service is available to ECMWF Member and Cooperating States only.