Mt. Etna, a volcano on the island of Sicily, erupted on October 26,
2002. Preliminary analysis of data taken by the Atmospheric Infrared
Sounder (AIRS) on NASA’s Aqua satellite on October 28 shows the
instrument can provide an excellent means to study the evolution and
structure of the sulfur dioxide (SO2) plume emitted from volcanoes.
These data also demonstrate that AIRS can be used to obtain the total
mass of SO2 injected into the atmosphere during a volcanic event,
information that may help us to better understand these dangerous
natural occurrences in the future.
The image above clearly shows the SO2 plume in shades of purple and black.
This image was created by comparing data taken at two different frequencies, or channels, and
creating one image that highlights the differences between these two
channels. Both channels are sensitive to water vapor, but one of the
channels is also sensitive to SO2. By subtracting out the common water
vapor signal in both channels, the SO2 feature remains and shows up as
an enhancement in the difference image.