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DWD provides monitoring information for all observations available to their DA system. However, in the case of surface pressure the model background value is not available if that observation is not used in the assimilation. Therefore, the surface pressure O-B departures cannot be calculated for that particular observation, and the O-B departures field is flagged (has missing value in the monitoring report) despite the fact that the observation itself has been made.
5.2. Combined (All)Anchor Section5.2 Section5.2
A summary combining all the performance reports from the different WIGOS monitoring centres is generated when option “All” is selected. This means that for each and every period, variable and monitoring category (availability and quality), there is a combined performance report available. The overarching rule for aggregating the information across NWP Centres is that the best data availability and quality result is used to generate a combined performance report. The combined availability performance report will be generated by taking the maximum availability result amongst all Centres (i.e. the information will come from the Centre with the highest total in the period). Regarding the quality, the result that will be retained is the one from the NWP model whose background field is closest to the observed value (i.e., the information will come from the Centre with the smallest O-B departures averaged over the period of interest).