In the near-real-time NWP module, the monitoring of data availability is based on performance figures obtained from comparing the observations received from the network to those required and expected to be ingested into the WMO Information System (WIS) according to the schedule determined from OSCAR/Surface metadata. In the Global Basic Observing Network (GBON) module, the monitoring of data availability performance is obtained by comparing the observations received from the GBON-affiliated stations to those expected in accordance with the GBON standard requirements (the shall provisions on Table 2.1 of EC-76/Doc. 3.2(3), ANNEX), where the expected frequency of observations is hourly for surface-based and 12-hourly for upper-air observations.The GBON list of stations is based on the list of stations assigned to GBON by WMO Members in OSCAR/Surface.
All targets regarding availability refer to the number of observations received by NWP centres from the network (Table 1). For each station, 6-hourly totals (section 4.1), daily totals (section 4.2), and monthly totals (section 4.3) are computed based on the quality monitoring information received from all the NWP Centres (section 5) and stored in the WDQMS Database. This task is performed on a daily basis, so that availability information of the observing network is accessible in near-real time. It is worth noting that in the WDQMS context “observations received” means the observations that were made available to the assimilation system of each NWP centre and are considered as a good proxy for the observations disseminated on the GTS. Moreover, the results are aggregated across NWP centres (section 5.2) to help reduce potential differences between the number of observations available on the GTS and the number of the observations seen by the individual assimilation systems.
Number of Expected Observations (based on OSCAR/Surface)
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) are extracted from OSCAR/Surface by using the “Schedule” element, and 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 entry in "Deployments" in OSCAR/Surface, a default schedule is assumed, which is 3 hourly observations for surface and 2 observations per day for upper-air stations, one in each interval, the 00 and 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, daily and monthly totals against the respective expected values for each observed variable (Table 2). A performance report is generated individually for each NWP Centre and time interval. For the 6-hourly totals, four reports are generated daily for each of the NWP centres.
GBON
The availability performance reports based on GBON targets are generated by comparing availability against expected values calculated for the different periods using the frequency rules mentioned above. This means that for surface observations, the expected observations are 6, 24 and 24 times the number of days in the month for the 6-hourly, daily, and monthly periods, respectively.
The GBON requirements for upper-air observations only apply to the daily and monthly aggregations, with a total of expected observations being 2 and twice the number of days in the month, respectively.
Table 1 - Availability
Definition | Number of observations per station as received by each NWP Centre during a defined period. |
Calculation | For each observed variable, the sum of all valid data is computed |
Valid data | Data not flagged as missing value |
Math expression |
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Table 2 - Availability performance
Definition | Number of observations per station as received by each NWP centre during a period divided by the number of expected for that period |
Calculation | Total of received observations per observed variable calculated as described in Table 1 divided by the sum of all expected observations for the period. |
Expected data | ‘International exchange schedule’ and ‘observation schedule’ obtained from OSCAR/Surface database |
Math expression | NValid ⁄NExpected ∗ 100%, where NValid is the maximum of Nj as described in Table 1 . |