Frequently Asked Questions (F.A.Q.)

1. How do I get access to the AMAP data (or any other restricted dataset)?

This information is generally available whenever you need it. If you try to download data that are marked as "Password protected", you will be asked for a username and password. Below is a "link", "How do I get access?" (move your mouse over the hyperlink), describing how to proceed. If data are not possible to download through the ACTRIS portal, you must follow the link (URL) on the left hand side of the data-set description for further information. Be aware that the same dataset is sometimes available both through a restricted database and through an open database. This is the case with OSPARCOM or AMAP data which are sometimes also made publicly available as EMEP data.

2. How recent is the data I can find in the ACTRIS portal?

This generally depends on which contributing database you are getting data from and on which type of data you are looking for. The metadata catalogue of the ACTRIS portal (which is what you access when you search for data) is generally updated once per day. Any new dataset in a contributing database will then be searchable through the portal maximum 24 hours later. For some of the contributing databases there are additional delays due to network rules for quality assurance before sharing of data. EARLINET and NDACC only provide publicly available data to the ACTRIS portal and their data are generally made public considerably after the measurement is performed - sometime sooner if the data owner asks for it. EMEP data are typically made available on an annual basis about 18 months after the end of a measurement year. Some of the ACTRIS data themselves are typically made available within weeks/months after the measurement is finished.

3. Why can I only download data from some of the databases through the ACTRIS portal?

This is either because the contributing database wants the user to access data through its own data portal or because the contributing database is technically unable to provide their data through the ACTRIS portal.

4. How do I select more than one entry in a selection box?

Hold down the CTRL-button while clicking to select more than one choice. Hold down the SHIFT-button to select multiple entries (from/to).

5. What types of data are available in the ACTRIS portal?

The majority of data available in ACTRIS portal are measurements/observational data. The measurements are typically made by remote sensing instrument (e.g. LIDAR) or an in-situ measuring instrument (e.g. ozone monitor). Data may be taken from a groundbased monitoring station, a balloon, an aircraft, a satellite, a ship, etc. The data are normally reported as a concentration (amount per volume) or as an integrated column value (often the case with some remote sensing instruments). In addition to observations, there are model data available. The ACTRIS portal contain data from all atmospheric composition disciplines including aerosol, greenhouse gas, stratospheric composition and reactive gas data.

6. How can I find observational data from a specific atmospheric event (e.g. transport of boreal forest fires emissions into Europe)?

If you are modelling a special atmospheric event you might be interested in any observational data you can find to validate whether or not your model is performing satisfactorily. A good approach is then to limit the search with the 4D boundary boxes above the map at the ACTRIS front page and not restrict the search any further. Please note that you do not need to fill in all fields – e.g. if you wish to study a transport event into the Arctic, it may be interesting to only limit the time (from date and to date) and minimum latitude.

7. On the "List Dataset" page, I see the "details" for each dataset, but information on altitude and start/stop time is sometimes missing or incomplete?

Most datasets are described with complete information regarding latitude/longitude/altitude/time. In some cases, it is not known when a measurement series ends (perhaps it is continuously running?) and this field is then kept open. In other cases, the altitude of the monitoring site is not reported and the altitude of the measurement is then not known. A similar case exists for some groundbased remote sensing observations (e.g. LIDARs) where there contributing database are unable to report on the height of the profile. We have chosen to include datasets where such metadata information is incomplete. Please note: If you e.g. limit your search to datasets between 1000 and 2000 meters in altitude, the "list datasets" may give you data with partly missing altitude information.

Known limitations

Lack of detailed start/stop information of some measurements.

Ideally, we try to insert the exact start and end time of an observation, e.g. the launch time of an ozone sonde and burst-time of its balloon (end time), so that it is possible to perform detailed searches on when there are data available. Unfortunately, only the start of a measurement series is available from some of the contributing databases. For ozone sondes, which are often launched once per week and measure for a few hours, this makes detailed searching more difficult.