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For each station, the expected 6-hourly and daily totals (i.e. the number of observations the station should exchange internationally via GTS/WIS during the defined period) is extracted from OSCAR/surface and made available to be used as a reference (Table 2). In this context, the schedule of observations is obtained for all the stations recorded in OSCAR/Surface that meet the following criteria: stations that are declared operational or partially operational on the level of the GOS/Regional Basic Synoptic Network (RBSN) affiliation; have an observation of the variable of interest; have the “international exchange” field set to “yes” (currently only for surface); are valid at the date of the defined period. For the upper-air, the schedule is obtained for all stations that are of station class Upper-air/Radiosonde. In case an observation has no deployment entry in “Deployments “ in OSCAR/Surface, a default schedule is assumed, which is of 3 hourly observations for surface and 2 daily observations per day for upper-air stations, one in each interval, the 00 and 12h 12 UTC interval. All the metadata used in WDQMS is updated daily, which means that any update on the station metadata recorded in OSCAR/surface will be reflected on the performance maps the next day.
The availability performance reports are generated by comparing the 6-hourly and daily totals against the respective expected values for each observed variable (Table 2). A performance report is generated individually for each NWP Centre and temporal time interval. For the 6-hourly totals, four reports are generated daily for each of the NWP centres.
GBON
The availability Availability is also compared against GBON requirements. According to the draft provisions, the expected frequency of observations is : hourly for surface-based and 12-hourly for the upper-air observations. The availability performance reports based on GBON targets are generated by comparing the availability against the expected values calculated for the different periods using the frequency rules mentioned above. This means that for surface observations, the expected data is 6 and 24 observations for 6-hourly and daily reports, respectively. For upper-air observations, the GBON requirements are only applied to the daily reports with a total of 2 observations expected.
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