1. The University of Reading Helen Dacre 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

2. The University of Reading Helen Dacre Introduction

3. 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 LevelConcentration (mg/m 3 ) High> 4 Medium0.2 - 2 Low< 0.2

4. The University of Reading Helen Dacre AIM: to compare NAME simulations of ash clouds with observations of ash clouds with a view to estimating the distal fine ash fraction (DFAF) Qualitative model evaluation Quantitative model evaluation Plume height Vertical distribution of ash Ash size distribution Future volcanic ash predictions Talk Outline

5. The University of Reading Helen Dacre Meteorology (Every 3 hours) 40 km resolution Global UM Eruption Source Parameters Height of eruption plume Vertical distribution of emitted ash Rate at which ash is emitted Ash size distribution Transport 3D wind fields Turbulent mixing Dry deposition Wet deposition Ash Concentrations (6-hourly averages) 0-20,000ft 20,000-35,000ft 35,000-55,000ft Operational VATD Modelling INPUT MODELOUTPUT Plume height (8.5km) Vertical ash distribution (uniform) Gardner et al.1995

6. The University of Reading Helen Dacre Qualitative Spatial Verification 12 UTC 16 th April MODIS visible 10 UTC 16 th April IASI Volcanic Ash Lieven Clarisse 12:24UTC 16 th April

7. The University of Reading Helen Dacre Quantitative Verification DFAF is defined as the % of the total emitted mass that is carried by small particles ( 1000km) from the volcano 50 km from volcano (Thor Thordarson)

8. 1. SENSITIVITY OF DFAF TO PLUME HEIGHT FLUCTUATIONS Comparison with ground-based lidars (Petersen and Arason, 2011) Mountain Missing Cloud

9. The University of Reading Helen Dacre DFAF at Leipzig and Chilbolton on 16 th April DFAF = 4%DFAF = 3% Robin Hogan Albert Ansmann, Ina Mattis

10. 2. SENSITIVITY OF DFAF TO VERTICAL DISTRIBUTION OF ASH Comparison with airborne lidars Uniform Concentrated

11. The University of Reading Helen Dacre DFAF on 17 th May uniform concentrated uniform concentrated Alan Grant, Franco Marenco Observed ash layers concentrated DFAF =1.6% uniform DFAF = 2.7%

12. The University of Reading Helen Dacre Comparison for all flights DFAF = 2% Alan Grant

13. 3. SENSITIVITY OF DFAF TO EFFECTIVE ASH SIZE DISTRIBUTION Comparison with in-situ aerosol measurements

14. The University of Reading Helen Dacre Distal FAF from in-situ measurements Average concentration on 14 th May 14 th May Size distribution on flightEffective ash size distribution 14 th May original DFAF = 2.8% new DFAF = 2.2% Ben Johnson

15. The University of Reading Helen Dacre DFAF Summary 3.5%

16. The University of Reading Helen Dacre GENERAL NAME identifies observed ash layers subject to possible timing and positioning errors due to meteorology Observed ash layers are thinner and lower than simulated layers SOURCE PARAMETER UNCERTAINTY Plume height - necessary to represent short-term fluctuations Vertical distribution - no best profile but related to activity Ash size distribution - Large percentage of < 10µm particles DFAF ~ 3.5% of the erupted mass was in ash particles small enough to allow long-range transport Future Volcanic Eruptions

17. EXTRA SLIDES

18. The University of Reading Helen Dacre Grimsvötn

19. The University of Reading Helen Dacre Ash Particles in Iceland 50 km from volcano (Thor Thordarson) 100µm

20. The University of Reading Helen Dacre Fine Ash Fraction at Chilbolton on 16 th April Robin Hogan faf = 2%

21. The University of Reading Helen Dacre FAAM Flights

22. The University of Reading Helen Dacre Fine Ash Particle Size Distribution 14 th May Size distribution on flightEffective-source size distribution 14 th May 17 th May original faf = 2.8% new faf = 2.2% original faf = 7.3% new faf = 3.4%

23. The University of Reading Helen Dacre Synoptic Analysis at 00UTC on 16 th April