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Geographic regions monitored in the Services
The SO2 column values are presented and delivered via the website in the
form of images (maps) and data files. There is no real difference between
the Volcanic SO2 and the Air Quality SO2 Service, other than that they focus
on different geographic regions. The Notification (or: Alert) Service or
exceptional SO2 concentrations of the Near-Real-Time (NRT) delivery monitors
each of these regions.
The size of the regions is determined on the one hand by the wish to zoom in
on sources of SO2 emissions and on the other hand by the geographical
coverage achived by the satellite instruments when passing through the
region: at least one orbit should pass through a region at any day.
The regions of the two Services partly overlap one another, which means that
SO2 emissions may be detected by both Services. As the measurement itself
cannot distinguish between possible sources of SO2 anyway, this is not a big
problem.
In addation to plots for the individual regions of both services, two more
plots are shown: one of the whole world shown in a cylindrical projection,
and one which shows the two poles from above.
Volcanic SO2 Service
For the Volcanic SO2 Service, a set of 42 geographic regions of 30 by 30 degrees covering known volcanoes has been defined. On the plots of the regions shown
on the website, only shows the volcanoes in that region that have erupted
since the year 1800, as listed on the website of the
Global Volcanism Programme (GVP).
The regions partly overlap one another, to ensure that SO2 emissions
from volcanoes near the edges of the regions are detected, whatever the wind
direction.
Air Quality SO2 Service
For the Air Quality SO2 Service, a set of
11 geographic regions of 40 by 40 degrees
covering industrialised areas has been defined.
There is no region defined for this Service over Southern America, because
of the detection problems associated with the South
Atlantic Anomaly.
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