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We have observed that daily and monthly SCIAMACHY data (from January to June 2009; from January to June 2010) have abnormally strong measurements;

see monthly plot of March 2010

We reprocessing these data. Do not hesitate to contact us if you want to know when reprocess will be finished.


Validation of the data products

Currently no real validation of SO2 slant column or vertical column densities has been undertaken as yet. A problem is that there are few ground-based measurements of SO2 that are appropriate for validation. It is planned to compare the results presented here with data from other satellite instruments. Furthermore, there is a close link with the NOVAC project, which intends to set up a network of ground-based stations for monitoring volcanic emissions of, among others, SO2.

In setting up and fine-tuning the SO2 slant column (SCD) retrieval with the DOAS method, the fitting results have been studied so as to optimise the settings for this retrieval. The slant columns have been compared to other results in an ad-hoc way for this, and in a few case studies. The SO2 SCD values can thus be considered to be fairly accurate, but a more rigorous quantitative validation is necessary.

The SO2 vertical column data (VCD) presented on the website are computed using an air-mass factor using look-up tables and an assumed height of the SO2 plume. This approach provides only a rough estimate of the value of the VCD. Hence, the values given for the VCD should not be taken as hard numbers.

The criteria for exceptional SO2 concentrations for the SO2 data have been set up by examining the results of the retrieval and analysis processes. The results of notification events found by the processing are the source for the continuous (qualitative) validation of the notification service.

  • In the near-real time service, the notification events are listed on dedicated web pages. At the bottom of these dedicated web pages there is room for adding notes and remarks, e.g. to link different notification to one and the same SO2 event, to link to external information, etc. This has to be done by hand and is therefore done on an an-hoc basis.

  • In the archive service, the processing provides an overview of notification cases for each month in the form of a table with some information on each SO2 peak event found. Most of this table is generated automatically, but there is room to add remarks and other info by hand to each table.
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