This dataset combines historic and ongoing N₂O observations across Europe from several networks and individual institutions.

The main purpose of the dataset is to provide input to atmospheric inversion of N₂O fluxes. As such only observations from the highest inlet were considered at tall tower sites. The dataset comprises observations from traditional GC-ECD systems as well as modern laser spectroscopy instruments. In addition to continuous observations, flask observations from the NOAA network were included.

Currently, total of 50 time series from 43 observing sites are included covering the period 2005 to the end of January 2024. Of these sites 28 were reporting continuous observations in 2023, although some of these (ICOS NRT) remain preliminary at the time of compilation. The data and metadata items were brought to the same format including a common flagging system and reporting of uncertainties. Additional outlier flagging may be applied by the user for additional filtering. Original network flags were maintained. Different elements of measurement uncertainty are reported by different networks/institutions. Depending on availability, three different components of uncertainty were maintained in the data reflecting standard deviation of the ambient observation during the observation interval, repeatability of working standards and combined uncertainty.

N₂O data are mostly reported on the WMO-X2006A calibration scale, with some exceptions reporting on the SIO-98 and SIO-16 scales, which were considered equivalent. However, additional site-to-site bias correction (< 0.5 ppb) may be required when using the data in inverse modelling.