The Prediction And Observation Of Volcanic Ash Clouds
The Prediction And Observation Of Volcanic Ash Clouds During The Eyjafjallajökull Eruption Helen Dacre and Alan Grant R. Hogan, D. Thomson, F. Marenco, B. Johnson, A. Ansmann, I. Mattis, L. Clarisse The University of Reading Helen Dacre
Talk Outline AIM: to compare NAME simulations of ash clouds with observations of ash clouds with a view to estimating the distal fine ash fraction (DFAF) n Qualitative model evaluation n Quantitative model evaluation ¡ Plume height ¡ Vertical distribution of ash ¡ Ash size distribution n Future volcanic ash predictions The University of Reading Helen Dacre
Qualitative Spatial Verification 12 UTC 16 th April IASI Volcanic Ash Lieven Clarisse MODIS visible 12: 24 UTC 16 th April The University of Reading 10 UTC 16 th April Helen Dacre
Quantitative Verification 50 km from volcano (Thordarson) n DFAF is defined as the % of the total emitted mass that is carried by small particles (<100μm diameter) and transported long distances (> 1000 km) from the volcano The University of Reading Helen Dacre
Mountain Missing Cloud (Petersen and Arason, 2011) 1. SENSITIVITY OF DFAF TO PLUME HEIGHT FLUCTUATIONS Comparison with ground-based lidars
DFAF at Leipzig and Chilbolton on 16 th April Albert Ansmann, Ina Mattis Robin Hogan DFAF = 4% The University of Reading DFAF = 3% Helen Dacre
Concentrated Uniform 2. SENSITIVITY OF DFAF TO VERTICAL DISTRIBUTION OF ASH Comparison with airborne lidars
DFAF on 17 th May uniform DFAF = 2. 7% Observed ash layers concentrated DFAF =1. 6% concentrated uniform concentrated Alan Grant, Franco Marenco The University of Reading Helen Dacre
Comparison for all flights DFAF = 2% Alan Grant The University of Reading Helen Dacre
3. SENSITIVITY OF DFAF TO EFFECTIVE ASH SIZE DISTRIBUTION Comparison with in-situ aerosol measurements
Distal FAF from in-situ measurements Average concentration on 14 th May Size distribution on flight 14 th May Ben Johnson The University of Reading Effective ash size distribution original DFAF = 2. 8% 14 th May new DFAF = 2. 2% Helen Dacre
DFAF Summary 3. 5% The University of Reading Helen Dacre
Future Volcanic Eruptions GENERAL n NAME identifies observed ash layers subject to possible timing and positioning errors due to meteorology n Observed ash layers are thinner and lower than simulated layers SOURCE PARAMETER UNCERTAINTY n Plume height - necessary to represent short-term fluctuations n Vertical distribution - no best profile but related to activity n Ash size distribution - Large percentage of < 10µm particles n DFAF ~ 3. 5% of the erupted mass was in ash particles small enough to allow long-range transport The University of Reading Helen Dacre
- Slides: 13