The WDQMS operational web tool monitors the performance of some of the WIGOS observing components, namely the GOS land-based surface and upper-air (radiosonde) stations and the GCOS upper-air land stations.
2.1. Near-real time NWP monitoring
The NWP module of the WDQMS web tool monitors the performance of all surface and upper-air (radiosonde) land stations documented in WMO’s database OSCAR/Surface, based on near-real-time monitoring information provided by DWD, ECMWF, JMA and NCEP. The system collects 6-hourly quality monitoring (QM) reports (CSV files in a commonly agreed format containing information for each observing station based on data assimilation results) from these four WIGOS Monitoring Centres and stores the data in the WDQMS database at ECMWF. Figure 1 shows a diagram of the QM data flow for the NWP module of the WDQMS web tool, where the database fed by the NWP QM reports and the web-based application constitute the back and front end of the QM system, respectively.
Figure 1 - Quality Monitoring (QM) data flow in the NWP module of the WDQMS web tool. The dashed arrow represents a feature to be added to the system in future releases.
2.1.1. Surface-land observations
ECMWF, DWD, NCEP and JMA are providing quality monitoring reports of land surface observations based on feedback from their data assimilation (DA) systems on a daily basis. These reports include qualitative and quantitative (Observation-minus-Background, O-B, departures) information covering the following observed physical quantities: surface pressure (or geopotential height for some high-altitude stations), 2-metre temperature, 2-metre relative humidity and 10-metre wind (meridional and zonal components). The qualitative information includes a description on the usage (Status, i.e., used or not used on the assimilation) and the type of report (i.e., the Traditional Alphanumeric Code -TAC-, or the Binary Universal Format for the Representation of Meteorological Data -BUFR) of each of the above mentioned physical quantities. It is worth noting that surface pressure is the most important in situ observed quantity for global NWP forecasting, and in some cases the only observed surface quantity over land used in the global atmospheric data assimilation, e.g. in the JMA global atmospheric data assimilation system (JMA, 2019). ECMWF’s atmopsheric 4D-Var also assimilates relative humidity over land at nighttime (Owens and Hewson, 2018). Based on these reports (four daily, centred at the main synoptic hours, 00, 06, 12 and 18UTC), it is possible to infer the performance of the land surface network both in terms of availability and quality.
2.1.2. Upper-air land observations
All the four WIGOS Monitoring Centres - ECMWF, DWD, JMA and NCEP- are providing quality monitoring reports for upper-air observations. Like the surface reports, these include qualitative as well as quantitative information. The quantitative information provided is obtained by aggregating the O-B departures into two main categories: layer between the first pressure level up to 100 hPa inclusive (Trop); and the layer from 100 hPa up to the last reported level (Stra). The quantitative information for the aforementioned layers consists of both the mean and standard deviation of O-B departures over the layer for the following observed physical quantities: upper-air temperature, upper-air humidity and upper-air wind. Provision of these data reports (four daily, centred at the main synoptic hours, 00, 06, 12 and 18UTC), typically happens 24 hours after the actual observation. The availability, quality and completeness of these conventional profiling observations can be easily assessed based on the information provided by the monitoring reports. It is worth mentioning that for the high-resolution BUFR reports, two messages are disseminated on the Global Telecommunication System (GTS): a preliminary message containing the measurements from the surface up to 100h Pa (TTAA=IUK header - I, Observational data Binary coded, U, upper-air message and S, radiosonde from fixed land station up to 100 hPa) and the final message containing the entire sounding from surface to balloon burst (TTAA=IUS, header - I, Observational data Binary coded, U, upper-air message and S, radiosonde from fixed land station up to balloon burst). ECMWF, JMA and DWD use the full BUFR message (i.e., IUS bulletin), and only if the full one is not available they use the IUK bulletin. Therefore, all NWP monitoring reports reflect this, i.e., the ascent report that contains the highest level will be used to calculate the statistics (i.e., IUS bulletin). This is a case of duplicates, however, if a radiosonde is launched 30 mins after the one that went wrong (i.e., burst at quite low altitudes), both will be used because they are not considered duplicates in those circumstances.
2.2. GCOS monitoring
The GCOS module of the WDQMS web tool monitors the performance of all upper-air (radiosonde) land stations that are part of the GCOS Upper-Air Network (GUAN) as documented in WMO’s database OSCAR/Surface, based on monthly monitoring information provided by DWD. The system collects two files monthly containing the availability and quality monitoring information separately.
2.2.1. Upper-air land observations
DWD is providing the monthly statistics reports for both availability and quality monitoring categories. The availability results for the GCOS upper-air stations are based on DWD data assimilation system, whereas the quality results provided by DWD are based on the O-B departures from ECMWF data assimilation system. The availability reports contain information on all GCOS upper-air stations regarding the number of radiosonde soundings that reach the 30hPa level in the reported month. The quality reports contain the root mean square of O-B departures calculated for the sounding profiles of the following observed quantities: upper-air temperature, upper-air humidity and upper-air wind. Provision of these data reports (monthly), typically happens 2 days after the end of the month. It is worth noting that contrary to the NWP monitoring, the monitoring of the GUAN stations only covers the radiosonde observations provided in the new Binary Universal Form for Representation of meteorological data (BUFR) reports.