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The Prediction And Observation Of Volcanic Ash Clouds During The Eyjafjallajökull Eruption

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. Talk Outline.

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The Prediction And Observation Of Volcanic Ash Clouds During The Eyjafjallajökull Eruption

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  1. The Prediction And Observation Of Volcanic Ash Clouds During TheEyjafjallajökull Eruption Helen Dacre and Alan Grant R. Hogan, D. Thomson, F. Marenco, B. Johnson, A. Ansmann, I. Mattis, L. Clarisse

  2. 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) • Qualitative model evaluation • Quantitative model evaluation • Plume height • Vertical distribution of ash • Ash size distribution • Future volcanic ash predictions

  3. Qualitative Spatial Verification 12 UTC 16th April IASI Volcanic Ash Lieven Clarisse MODIS visible 12:24UTC 16th April 10 UTC 16th April

  4. Quantitative Verification 50 km from volcano (Thor Thordarson) • DFAF is defined as the % of the total emitted mass that is carried by small particles (<100μm diameter) and transported long distances (> 1000km) from the volcano

  5. (Petersen and Arason, 2011) 1. Sensitivity of DfAF to plume height fluctuations Mountain Missing Cloud Comparison with ground-based lidars

  6. DFAF at Leipzig and Chilbolton on 16th April Albert Ansmann, Ina Mattis Robin Hogan DFAF = 4% DFAF = 3%

  7. Concentrated Uniform 2. Sensitivity of DFAF to vertical distribution of ash Comparison with airborne lidars

  8. DFAF on 17th May Observed ash layers concentrated uniform uniform concentrated uniform DFAF = 2.7% concentrated DFAF =1.6% Alan Grant, Franco Marenco

  9. Comparison for all flights DFAF = 2% Alan Grant

  10. 3. Sensitivity of DfAF to EFFective ash size distribution Comparison with in-situ aerosol measurements

  11. Distal FAF from in-situ measurements Average concentration on 14th May Size distribution on flight Effective ash size distribution 14th May original DFAF = 2.8% 14th May new DFAF = 2.2% Ben Johnson

  12. DFAF Summary 3.5%

  13. Future Volcanic Eruptions 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

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