The data quality monitoring practices are based on the assessment of the performance of observational systems against a set of targets defined for the three performance measures -availability, timeliness and quality - that are proposed in the Technical Guidelines for Regional WIGOS Centres on the WIGOS Data Quality Monitoring System (WMO, 2018) hereafter called WDQMS Guidance Document. The current version of the web tool provides only monitoring of availability and quality for land-based surface and upper-air observations.