 |
| Titel |
Optical, microphysical and compositional properties of the Eyjafjallajökull volcanic ash |
| VerfasserIn |
A. Rocha-Lima, J. V. Martins, L. A. Remer, N. A. Krotkov, M. H. Tabacniks, Y. Ben-Ami, P. Artaxo |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 19 ; Nr. 14, no. 19 (2014-10-10), S.10649-10661 |
| Datensatznummer |
250119089
|
| Publikation (Nr.) |
 copernicus.org/acp-14-10649-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| Better characterization of the optical properties of aerosol particles are an
essential step to improve atmospheric models and satellite remote sensing,
reduce uncertainties in predicting particulate transport, and estimate
aerosol forcing and climate change. Even natural aerosols such as mineral
dust or particles from volcanic eruptions require better characterization in
order to define the background conditions from which anthropogenic
perturbations emerge. We present a detailed laboratorial study where the
spectral optical properties of the ash from the April–May (2010)
Eyjafjallajökull volcanic eruption were derived over a broad spectral
range, from ultra-violet (UV) to near-infrared (NIR) wavelengths. Samples of
the volcanic ash taken on the ground in the vicinity of the volcano were
sieved, re-suspended, and collected on filters to separate particle sizes
into fine and mixed (coarse and fine) modes. We derived the spectral mass
absorption efficiency αabs [m2g−1] for fine and
mixed modes particles in the wavelength range from 300 to 2500 nm
from measurements of optical reflectance. We retrieved the imaginary part of
the complex refractive index Im(m) from αabs,
using Mie–Lorenz and T-matrix theories and considering the size distribution
of particles obtained by scanning electron microscopy (SEM), and the grain
density of the volcanic ash measured as
ρ = 2.16 ± 0.13 g cm−3. Im(m) was found
to vary from 0.001 to 0.005 in the measured wavelength range. The dependence
of the retrieval on the shape considered for the particles were found to be
small and within the uncertainties estimated in our calculation. Fine and
mixed modes were also analyzed by X-ray fluorescence, exhibiting distinct
elemental composition supporting the optical differences we found between the
modes. This is a comprehensive and consistent characterization of spectral
absorption and imaginary refractive index, density, size, shape and elemental
composition of volcanic ash, which will help constrain assumptions of ash
particles in models and remote sensing, thereby narrowing uncertainties in
representing these particles both for short-term regional forecasts and
long-term climate change. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|