presentation slides; els 2013
TRANSCRIPT
Scattering of Palagonite,
Mars analog dust,
Modeled with Ellipsoids
ELS XIV, 17 – 21 June, 2013, Lille, France
Sini Merikallioa, T. Nousiainena,b, M. Kahnertc,d, A.-M. Harria
aFinnish Meteorological Institute, P.O. Box 503, 00101
Finland, [email protected] BHelsinki University, Finland cSwedish Meteorological and Hydrological Institute,
Folkborgsvägen 17, 60176 Norrköping, Sweden dChalmers University of Technology, 41296
Gothenburg
Objectives
1. Testing suitability of ellipsoids to model
mars analog dust particle single scattering
properties. Achieved by comparing to
measured laboratory data.
2. Testing relative
impacts of refractive
index, size and shape distribution.
Measurements by Laan et. al., Icarus 199, 2009
Mars dust
Reff = 1.6 um,
m = 1.5 + 0.002 (1000 nm)
upto 1.5 + 0.015 (320 nm).
@ lambda = 320, 500, 1000 nm
Palagonite
Reff = 4.5 um – 11.1 um,
m = 1.6 + 0.0001i
@ lambda = 632.8 nm
Values from Wolff et. al., JGR 114, 2009
and Wolff et. al. Icarus 208, 2010
Tool: Theory The scattering of an ensemble of randomly oriented
particles can be described by a scattering matrix:
(For spheres: F11 = F22 and F33 = F44)
Stokes vector scattering matrix
in
in
in
in
4434
3433
2212
1211
sc
sc
sc
sc
V
U
Q
I
FF00
FF00
00FF
00FF
V
U
Q
I
Stokes vector
Ellipsoids
• Database of Meng et. al. J. Aerosol. Sci. 41, 2010.
Bi et. Al., Applied Optics 48, 2008
– Same database used for
Earth atmospheric dust.
• How well does it work?
• With what kind of shape distribution?
Shape
distribution
best for each element.
X best for the whole matrix
•
scattering angle θ scattering angle θ
spheroid best fit, sphere, x Measurements,
individual ellipsoids, ellipsoid best fit
Osa 2 –> move to Mars
Single scattering
albedo ω
Asymmetry
parameter g
Mie Best-Fit Equiprobable n3 n3 spheroids
Mie Best-Fit Equiprobable n3 n3 spheroids
Conclusions
Ellipsoids, even more then spheroids, improve greatly on Mie-models.
Good fits, but different optimal shape distributions for different scattering matrix elements makes it hard to suggest a universally optimal shape distribution.
Study submitted to Optics Express.
