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.

1988

GEOPHYSICAL RESEARCH LETTERS

RETRIEVAL

CLOUDS

ATA AJ

EXTINCTION SPECTRA

DISCRETE-DIPOLE APPROXIMATION

LIGHT-SCATTERING

1989

1973

LLACK JB

V19

APPLIED OPTICS

V16

SPACE

RADIATIVE-TRANSFER CALCULATIONS

P372

AEROSOLS

P1293

V27

GLASSES

ICARUS

AMNES K

P2502

Författare

A. Kylling

Norsk institutt for luftforskning (NILU)

Michael Kahnert

Chalmers, Rymd- och geovetenskap, Global miljömätteknik och modellering

H. Lindqvist

Helsingin Yliopisto

T. Nousiainen

Finnish Meteorological Institute

Helsingin Yliopisto

Atmospheric Measurement Techniques

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

Vol. 7 4 919-929

Ämneskategorier

Meteorologi och atmosfärforskning

DOI

10.5194/amt-7-919-2014