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| Titel |
Observing Sarychev Peak volcanic aerosols with high-resolution infrared limb emission spectra from the MIPAS-E instrument: plume transport and stratospheric sulphate signatures. |
| VerfasserIn |
Harjinder Sembhi, John Remedios, Timothy Trent, David Moore, Reinhold Spang, Mike Fromm |
| 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 |
250057244
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| Zusammenfassung |
| Volcanic eruptions can release large volumes of sulphur dioxide (SO2), mineral ash, water
vapour, sulphate aerosols and other atmospheric constituents directly into the upper
troposphere and lower stratosphere (UTLS). On the 11th of June 2009, Sarychev Peak
volcano (48ºN, 153ºE) located on Kuril Islands, Russia, began a series of eruptions ejecting
ash plumes into the atmosphere and resulting in a widespread stratospheric aerosol layer
forming across the Northern Hemisphere. The Sarychev Peak eruptions provide an excellent
opportunity to observe and model the full sulphuric acid (H2SO4) spectrum and in particular
we present the first hemispheric observations of thermal infrared emission spectra of
H2SO4.
Many nadir remote sensors have provided essential measurements on the transport and
dispersion of volcanic plumes (e.g. OMI, MODIS, AVHRR). Prominent among these are
nadir infrared sounders that make dedicated SO2 retrievals using simple spectral detection
methods (e.g. IASI). Such instruments cannot give accurate injection heights and cannot
easily separate stratospheric and tropospheric effects due to their broad vertical
resolution. Limb sounding instruments and space-based Lidar such as NASA’s
CALIPSO mission provide alternative methods which can give more detailed height
information.
The thermal infrared spectrum from 700 to 1200 cm-1 (~14 to 8.3 microns) captures the
distinct emission/absorption signatures of ash, SO2, H2SO4 aerosols and ice. Limb sounding
Fourier Transform spectrometers provide high-resolution thermal emission spectra with
typically 2 to 3 km vertical resolution in the UTLS making them well suited to study volcanic
events. Not only do such measurements detail the vertical distribution and transport pathways
but the emission spectra themselves can reveal details about plume composition with
the potential to distinguish aerosol particle radius size and formation/conversion
timescales.
One such instrument is the Michelson Interferometer for Passive Atmospheric Sounding
(MIPAS-E) launched on ESA’s ENVISAT platform in March 2002. With a spectral resolution
of 0.0625 cm-1 (unapodised) and nominal 1.5 km vertical sampling, MIPAS-E spectra
encapsulate volcanic signatures well into the stratosphere. A particle-detection algorithm
designed at the University of Leicester has successfully identified volcanically influenced
measurements by accounting for the strong aerosol, ice and cloud absorption signals that
manifests in MIPAS-E spectra. In this investigation the algorithm is applied to reprocessed
MIPAS-E (version 5) level 1b spectra from June to August 2009 and the following results
will be presented:
Plume and cloud top heights for June to August 2009 capturing the initial plume
injection as high as 22 km and hemispheric transport over this period.
Comparison of MIPAS to the 532 nm total backscatter measurements from the
CALIOP instrument for a verification of plume height and Northern Hemisphere
stratospheric aerosol layer.
Observations of the evolving H2SO4 emission spectra to identify volcanic
aerosol signatures in the high resolution MIPAS measurements and mapping
their changing characteristics during the conversion process. |
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