The WIGOS Data Quality Monitoring System (WDQMS) web tool is the result of efforts by the ICG-WIGOS Task Team on WDQMS and of ECMWF (Prates and Richardson 2016), which further developed the web tool and hosts it with the support of MeteoSwiss and the WMO Secretariat (WMO, 2019). The current operational version of the WDQMS web tool provides three monitoring modules: the “Near-real-time NWP monitoring of the Global Observing System (GOS) networks”, the “Global Basic Observing Network (GBON)“ and the “Monitoring of the Global Climate Observing System (GCOS) networks”. The first module includes the NWP-based monitoring of GOS land-based surface and upper-air (radiosonde) observations as well as the marine surface observations. The monitoring categories, availability and quality, are based on near-real-time monitoring information provided by four participating global numerical weather prediction (NWP) centres: the German Weather Service (DWD), the European Centre for Medium-Range Weather Forecasts (ECMWF), the Japan Meteorological Agency (JMA), and the US National Centers for Environmental Prediction (NCEP). The system aggregates NWP monitoring information by station, time interval, observed variable and NWP Centre and generates availability and quality performance reports that are displayed as maps or time series. It should be noted that the marine surface component monitors only quality, which currently is based on information from two NWP Centres (ECMWF and DWD) only. The second module monitors all GBON- affiliated surface land stations and upper-air stations on land.  This module assesses GBON station-level compliance using data availability as the primary performance measure. The near-real-time monitoring information provided by the four NWP Centres is aggregated by station, variable, and time interval, and the calculated total number of reports are compared against the corresponding thresholds defined by the compliance criteria for the different station types.  The third monitoring module is based on data collected from GCOS monitoring centres and includes the monitoring of both GCOS Surface Network (GSN) and GCOS Upper-Air Network (GUAN). The GCOS monitoring is based on monthly statistics provided by DWD.

This User Guide is organized according to the entries and options available on the control panel of the WDQMS web tool to facilitate the users’ search of a particular option. Information on the monitoring module options as well as on monitoring categories are described  sections 2 and 3, respectively. Details of the temporal aggregation are given in section 4, and information about the participating NWP Centres in section 5. Finally, a summary of the products (maps and time series) available for the three monitoring modules covered by the tool is presented in section 6,  section 7 and section 8, and the References are included in section 9.