Environmental Engineering Reference
In-Depth Information
9
Satellite and aircraft-based techniques to measure
volcanic emissions and hazards
david pieri
9.1 Introduction
The outstanding utility of volcanological remote sensing techniques is their ability
to provide synoptic data at a variety of spatial scales, often coupled, as in the case of
orbital data, with relatively easy repeat access to address dynamic processes,
mitigated only by atmospheric obscuration. Volcanic phenomena on the Earth
span a range of spatial scales, characteristic activity frequencies, compositions,
mass eruption rates, and emitted energies, a catalog well known to volcanologists:
explosive and effusive eruptions, passive emissions, and submarine eruptions (often
at enormous hydrostatic pressures), and outliers like natrocarbonatite eruptions,
mud volcanoes, and hydro-geothermal
field emissions. This expansive phenomeno-
logical range of volcanism, across a range of temperatures (e.g.
~
1450K (lavas) to
~
200K (lofted stratospheric ash)), and its relentless dynamism, poses substantial
challenges for the application of remote sensing technology.
Spatial scales and recurrence frequencies of contemporary volcanic environmental
effects (see also
Chapters 13
and
14
) are demanding in terms of remote sensing
techniques. For example, within the planetary boundary layer (1
-
3 km above sea
level (ASL) generally), eruption columns and plumes can inject ash and other
aerosols (e.g. H
2
SO
4(liquid)
,CaSO
4(solid)
) on timescales from minutes to hours, and
can persist for days (continuously), for months (intermittently). Above the tropopause,
post-explosive-eruption stratospheric (
10,000 m above sea level (ASL)) ash and
gas clouds (especially sulfate nano-aerosols) can drift thousands of kilometers,
occasionally circumnavigating the globe, playing havoc with aviation, and altering
the Earth
~
s surface insolation while heating the stratosphere, sometimes for months,
or even years. Depletion of the planetary ozone shield by almost 10% occurred after
the eruption of Mt. Pinatubo (1991). Repose periods between such large events can
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