Volcanic ash infrared signature: porous non-spherical ash particle shapes compared to homogeneous spherical ash particles
Artikel i vetenskaplig tidskrift, 2014

The reverse absorption technique is often used to detect volcanic ash clouds from thermal infrared satellite measurements. From these measurements effective particle radius and mass loading may be estimated using radiative transfer modelling. The radiative transfer modelling usually assumes that the ash particles are spherical. We calculated thermal infrared optical properties of highly irregular and porous ash particles and compared these with mass-and volume-equivalent spherical models. Furthermore, brightness temperatures pertinent to satellite observing geometry were calculated for the different ash particle shapes. Non-spherical shapes and volume-equivalent spheres were found to produce a detectable ash signal for larger particle sizes than mass-equivalent spheres. The assumption of mass-equivalent spheres for ash mass loading estimates was found to underestimate mass loading compared to morphologically complex inhomogeneous ash particles. The underestimate increases with the mass loading. For an ash cloud recorded during the Eyjafjallajokull 2010 eruption, the mass-equivalent spheres underestimate the total mass of the ash cloud by approximately 30% compared to the morphologically complex inhomogeneous particles.

AMNES K

P372

LLACK JB

GEOPHYSICAL RESEARCH LETTERS

ATA AJ

LIGHT-SCATTERING

V16

V19

RETRIEVAL

P2502

CLOUDS

1989

RADIATIVE-TRANSFER CALCULATIONS

APPLIED OPTICS

ICARUS

1988

P1293

AEROSOLS

SPACE

DISCRETE-DIPOLE APPROXIMATION

1973

EXTINCTION SPECTRA

V27

GLASSES

Författare

A. Kylling

Norsk institutt for luftforskning (NILU)

Michael Kahnert

Chalmers, Rymd- och geovetenskap, Global miljömätteknik och modellering

H. Lindqvist

Helsingin Yliopisto

T. Nousiainen

Helsingin Yliopisto

Finnish Meteorological Institute

Atmospheric Measurement Techniques

1867-1381 (ISSN) 1867-8548 (eISSN)

Vol. 7 919-929

Ämneskategorier

Meteorologi och atmosfärforskning

DOI

10.5194/amt-7-919-2014