 |
| Titel |
Physical and optical properties of 2010 Eyjafjallajökull volcanic eruption aerosol: ground-based, Lidar and airborne measurements in France |
| VerfasserIn |
M. Hervo, B. Quennehen, N. I. Kristiansen, J. Boulon, A. Stohl, P. Fréville, J.-M. Pichon, D. Picard, P. Labazuy, M. Gouhier, J.-C. Roger, A. Colomb, A. Schwarzenboeck, K. Sellegri |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 4 ; Nr. 12, no. 4 (2012-02-16), S.1721-1736 |
| Datensatznummer |
250010721
|
| Publikation (Nr.) |
 copernicus.org/acp-12-1721-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| During the Eyjafjallajökull eruption (14 April to 24 May 2010), the
volcanic aerosol cloud was observed across Europe by several airborne in
situ and ground-based remote-sensing instruments. On 18 and 19 May, layers
of depolarizing particles (i.e. non-spherical particles) were detected in
the free troposphere above the Puy de Dôme station, (PdD, France) with a
Rayleigh-Mie LIDAR emitting at a wavelength of 355 nm, with parallel and
crossed polarization channels. These layers in the free troposphere (FT)
were also well captured by simulations with the Lagrangian particle
dispersion model FLEXPART, which furthermore showed that the ash was
eventually entrained into the planetary boundary layer (PBL). Indeed, the
ash cloud was then detected and characterized with a comprehensive set of in
situ instruments at the Puy de Dôme station (PdD). In agreement with the
FLEXPART simulation, up to 65 μg m−3 of particle mass and 2.2 ppb
of SO2 were measured at PdD, corresponding to concentrations higher
than the 95 percentile of 2 yr of measurements at PdD. Moreover, the
number concentration of particles increased to 24 000 cm−3, mainly in
the submicronic mode, but a supermicronic mode was also detected with a
modal diameter of 2 μm. The resulting optical properties of the ash
aerosol were characterized by a low scattering Ångström exponent
(0.98), showing the presence of supermicronic particles. For the first time
to our knowledge, the combination of in situ optical and physical
characterization of the volcanic ash allowed the calculation of the
mass-to-extinction ratio (η) with no assumptions on the aerosol
density. The mass-to-extinction ratio was found to be significantly
different from the background boundary layer aerosol (max: 1.57 g m−2
as opposed to 0.33 ± 0.03 g m−2). Using this
ratio, ash mass concentration in the volcanic plume derived from LIDAR
measurements was found to be 655 ± 23 μg m−3 when the plume was
located in the FT (3000 m above the sea level – a.s.l.).
This ratio could also be used to retrieve an aerosol mass concentration of
579 ± 60 μg m−3 on 19 April, when LIDAR observations detected
the ash cloud at 3000 m a.s.l. in correspondence with model simulations
(FLEXPART). On 22 April, another ash plume entered the BL, and although it
was more diluted than during the May episode, the French research aircraft
ATR42 that passed over Clermont-Ferrand in the PBL confirmed the presence of
particles with a supermicronic mode, again with a modal diameter at 2 μm.
This data set combining airborne, ground-based and remote sensing
observations with dispersion model simulations shows an overall very good
coherence during the volcanic eruption period, which allows a good
confidence in the characteristics of the ash particles that can be derived
from this unique data set. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|