Background information on E-OBS version 2.0

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The E-OBS gridded daily dataset is based on the daily station series available in the European Climate Assessment & Dataset project. The ECA&D database has seen a major software update in July 2009. This means that the programs and scripts that are behind the database are rewritten. This was needed to improve and to shorten the time needed to update the database when new data is added. As part of this, the programs that produce the blended station series have been improved as well. Blended means that missing days from series are filled in or extended with data from series of nearby stations. These stations should be less than 25 km away and have less than 50 meter height differences. Also synoptical stations with these conditions are used to extend the series for the most recent years. We decided to produce blended series for each individual station instead of station groups which was done before. The gridding process uses these blended series. Because now we have blended series for each individual station, we have used all the available blended series in this new version of E-OBS and not only those for stations groups which was done in the previous release.

For several stations we have multiple series of the same element where one series is provided by a participant and another by a project. We have seen that there can be large differences in these series although they are given for the same location. We assume that the participant series have undergone a better validation process and therefore we have more confidence in these series. To account for this, the blending process is changed also to give preference to participant data (where available) over project data.

For some stations (for example in Spain) the participant asked us to replace the series we had with new ones due to errors. We also corrected some error codes from participants/projects that did not use -9999, which remained in the dataset after including the participant/project data. A few mistyped station locations where corrected and new stations in Norway, the Netherlands, Germany, Northern Italy and Serbia are included.

All of this can lead to differences between the old version of E-OBS and the new one. Therefore, we would like to encourage users to use this new version of E-OBS.