The University of Reading Helen Dacre The Eyjafjallajökull eruption: How well were the volcanic ash clouds predicted? Helen Dacre and Alan Grant Robin Hogan, Dave Thomson, Ben Devenish, Jim Haywood, Franco Marenco, Ben Johnson, Albert Ansmann, Ina Mattis and Lieven Clarisse
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The University of Reading Helen Dacre The Eyjafjallajökull eruption: How well were the volcanic ash clouds predicted? Helen Dacre and Alan Grant Robin.
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The University of Reading Helen Dacre
The Eyjafjallajökull eruption: How well were the volcanic ash clouds predicted?
Helen Dacre and Alan Grant
Robin Hogan, Dave Thomson, Ben Devenish, Jim Haywood, Franco Marenco, Ben Johnson, Albert Ansmann, Ina Mattis and Lieven Clarisse
The University of Reading Helen Dacre
Motivation
The University of Reading Helen Dacre
EUROCONTROL report from 14 - 20 April: 75% of European airspace closed 100,000 flights cancelled 10 million passenger journeys affected 7000 flights cancelled up to 18 May
Motivation
Level Concentration (mg/m3)
High > 4
Medium 0.2 - 2
Low < 0.2
The University of Reading Helen Dacre
Operational volcanic ash transport and dispersion (VATD) models
Quantitative model predictions
Source parameter uncertainty
Meteorological input uncertainty
Future Work
Talk Outline
The University of Reading Helen Dacre
Operational VATD Modelling
INPUT MODEL OUTPUT
The University of Reading Helen Dacre
0.1 0.55
20
70
4.4
0
20
40
60
80
% o
f tot
al m
ass
Particle Diameter (µm)
0.1-0.3
0.3-1
1-3
3-10
10-30
30-100
Eyjafjallajökull Source Parameters
0.225H=0.365M
H
The University of Reading Helen Dacre
Column Integrated Mass Concentration 14-18th April
The University of Reading Helen Dacre
Fine-ash Fraction?
Mastin et al. (2009)
COMPARISON WITH GROUND BASED LIDAR
The University of Reading Helen Dacre
IASI Volcanic Ash Product
12UTC 16th April00UTC 16th April
Leipzig
10UTC 16th April22UTC 15th April
L. Clarisse
Leipzig Leipzig
Leipzig
The University of Reading Helen Dacre
1.5%
Scaling to Observed Concentration at Leipzig
A. AnsmannI. Mattis
The University of Reading Helen Dacre
MODIS Visible Image
12UTC 16th April
12:24UTC 16th April10:44UTC 16th April
Chilbolton
(Hogan et al. 2011)
The University of Reading Helen Dacre
Scaling to Observed Concentration at Chilbolton
(Hogan et al. 2011)
The University of Reading Helen Dacre
5-minute time series of plume height from the Icelandic radar (data from Petersen and Arason)
It is possible to identify the ash layers detected with the ground based and airborne lidars with layers in the NAME simulations
Observed ash layers are thinner than teh simulated layers and at lower altitude
Horizontal and vertical structure of the simulated ash clouds are sensitive to assumptions about the profile of the ash emissions – no best profile but for weak activity a uniform profile may be best but for greater activity a concentrated profile better
Quantitative comparison suggests that only about 3.5% of the erupted mass was in ash particles small enough to allow long-range transport
It is necessary to represent the large, short-term fluctuations in plume height accurately
Summary
The University of Reading Helen Dacre
NAME did a reasonable job of capturing the horizontal structure of the ash cloud subject to possible timing and positioning errors that occur due to meteorology
NAME underestimates maximum concentrations by a factor of about 2.5
OR NAME overestimates layer with by a factor of 2.5 Default particle size distribution in NAME contains too
many 10-30µm diameter particles
Summary
The University of Reading Helen Dacre
Operational volcanic ash dispersion modelling Model input uncertainty
Eruption plume height, vertical distribution Peak concentrations Fine ash fraction Particle size distribution