Observations are essential for numerical weather prediction (NWP) systems. They are used by the data assimilation system to produce the best estimate of the initial conditions (analysis). The quality of the analysis and the subsequent forecasts depend, amongst other factors, on the quality and availability of observations. To ensure optimal use of observations timely detection of availability and quality issues is necessary to trigger mitigation actions.  On this space we keep chronological record of data events that affected the observing system used at ECMWF. Such information might be of interest to ECMWF's forecast users and to the wide NWP community. The estimated  impact of these events on the analysis/forecast is not systematically assessed and therefore not included. The list is updated manually on a regular and best effort basis. It includes only the main events and new additions/cessation of data. If you have related questions please contact the email address below (reply is on best effort basis)