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| Titel |
Early in-flight detection of SO2 via Differential Optical Absorption Spectroscopy: A feasible aviation safety measure to prevent potential encounters with volcanic plumes |
| VerfasserIn |
Leif Vogel, Bo Galle, Christoph Kern, Hugo Delgado Granados, Ulrich Platt |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250054924
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| Zusammenfassung |
| Volcanic ash is a threat to aviation, mainly to jet engines with the risk of total engine failure.
Other risks include abrasion of windshields and damage to avionic systems. These threats
have been widely recognized since the early 1980s, when volcanic ashes provoked several
near fatal incidents of engine failure of jet aircrafts (e.g. Mt. St. Helens, USA, 1980; Mt.
Galunggung, Indonesia, 1982 and Redoubt volcano, USA, 1989). In addition to volcanic ash,
also volcanic gases pose a threat. Prolonged and/or cumulative exposure of sulfur
dioxide (SO2) or sulfuric acid (H2SO4) aerosols potentially affects e.g. windows and
airframes, and damage to engines has been recorded. SO2 receives most attention
because its presence above the lower atmosphere is a clear proxy for a volcanic
plume and indicates that fine ash could also be present. One of the most recent
examples of volcanic ash impairing aviation is the eruption of Eyjafjallajökull, Iceland,
between March and May 2010, which led to temporal closure of the European air
space. Although no severe incidents were reported, it affected an unprecedented
number of people and economic losses are estimated to amount up to U.S. $1.7
billion.
Up to now, remote sensing of SO2 via Differential Optical Absorption Spectroscopy (DOAS)
in the ultraviolet spectral region has primarily been used to measure volcanic clouds from
satellites and ground-based platforms. Here we present a set of experimental and modelled
data showing the feasibility of DOAS to be used as an airborne early detection system of SO2
distributions in two spatial dimensions. In order to prove the concept, simultaneous airborne
and ground-based measurements were conducted at Popocatépetl volcano, Mexico, in April
2010. Popocatépetl is especially suited because its summit is at 5426m above sea level, thus
volcanic gases are emitted above the boundary layer and at altitudes which allow extracting
significant conclusions from the measurements because of its proximity to typical traffic
airspace.
Ground based observations consisted of stationary instruments and traverse measurements,
allowing to obtain plume height and wind direction relative to the source. The plume of
Popocatépetl extended at an altitude around 5250m a.s.l., and was approached and passed
through at the same flight level with forward looking DOAS systems aboard an airplane.
These DOAS systems measured SO2 in the flight direction and at 40mrad angles
in both horizontal and vertical directions relative to it. The approaches started at
distances up to 25 km from the plume and SO2 was measured at all times well
above the detection limit. The observations are combined with radiative transfer
studies modelling the conditions at hand. The experimental data validate the radiative
transfer modelling results. They indicate that, depending on flight height, an extended
volcanic plume with a SO2 concentration of 1012 molec/cm2 can be detected at
distances up to 80km away, providing a tool of early warning to pilots in order to
avoid potentially dangerous approaches to aircraft-threatening volcanic plumes. |
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