All observations which are assimilated by a numerical weather prediction are controlled on the basis of statistics relating to the difference between the observation and the model. Thus, each observations available and useful for ARPEGE model is compared with a six hours range forecast (first-guess) interpolated at the point of observation and for the same validity date. Observations whose statistics deviate notably from the average behavior of the other observations compared to the first-guess are regarded as suspect.

METEO-FRANCE produces monitoring statistics on the quality of observations received at Toulouse and which are assimilated by ARPEGE model.
The following site provides information on various types of observation and are of several types :

data coverage maps : distribution of available and used observations on the globe

DFS : "Degree of Freedom Signal" which quantify the power of an observation type to modify assimilation system
satellite observations : quality of geostationary and polar orbiting wind data (SATOB), geostationnary and polar orbiting brightness temperature data (ATOVS AMSU-A, HIRS and AMSU-B channels, AIRS, IASI, SSMIS and SEVIRI channels), sea surface wind data (scatterometer), zenithal total delay data (ground GPS stations) through daily monitoring statistics time series and radio-occultation data (GPS satellite) through daily monitoring statistics time series.
An automatic satellite data checking system (auto-alerts service) has also been implemented at METEO-FRANCE in order to produce alarm messages if an anomaly is detected in the quality or the availability of the satellite data assimilated by the model.