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Volcanic Ash Detection and Prediction at the Met Office

Volcanic Ash Detection and Prediction at the Met Office. Responsibilities Tools Etna 2002 Future. Helen Champion, Sarah Watkin Derrick Ryall. Met Office is the London VAAC. VAAC = Volcanic Ash Advisory Centre. Satellite ash detection products. AVHRR ch4 (10.8 m ) - ch5 (12.0 m )

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Volcanic Ash Detection and Prediction at the Met Office

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  1. Volcanic Ash Detection and Prediction at the Met Office • Responsibilities • Tools • Etna 2002 • Future Helen Champion, Sarah WatkinDerrick Ryall

  2. Met Office is the London VAAC VAAC = Volcanic Ash Advisory Centre

  3. Satellite ash detection products • AVHRR • ch4 (10.8 m) - ch5 (12.0 m) • available within 30 mins • Covers three areas: • Mediterranean area (Mt. Etna) • London VAAC • Iceland • Frequency • 3 hourly over Iceland • 6 hourly over the Mediterranean 28 October 2002 1316 UTC

  4. AVHRR London VAAC (ch4 -ch5)

  5. Met Office NAME model • Dispersion model • Predicts the transport of airborne pollutants • 1-1000’s km, hours - days • Lagrangian particle model • Emergency response • nuclear, volcano, fire, FMD • Air pollution • episodes, forecasts, chemistry • Source attribution • where, when, how much • source/receptor relationships • CTBTO

  6. Volcanic Ash Graphics • Three levels • FL350-FL550 • FL200-FL350 • Surface-FL200 • Source • Unit release • between summit height and plume top • assumes particle size distribution • T+6,12,18,24 • Extent of ‘visible’ ash cloud

  7. Additional Volcanic Ash graphics • Contoured plumes • Six levels • Easier comparisons with imagery / observations

  8. Recent Improvements to NAME • Automated plotting threshold for visual ash cloud concentrations • Previously manual forecaster input based on obs • Upgraded to use ‘New Dynamics’ version of Unified Model • 3 hourly global fields to T+144, ~60km resolution • Increased vertical resolution (particularly near tropopause) • Revised boundary layer turbulence schemes

  9. Volcanic Ash - Trajectories • Also provide trajectories • Follow mean wind • Start at several levels • Quick indication of plume spread at various levels

  10. IcelandDaily runs • Improve response times and preparedness • Daily simulations using NAME • Release from Katla • 6 hour release • 0, 6, 12 & 18Z • surface to FL400 • Output on six levels

  11. Etna eruption 2002 • 27 Oct 2002 Etna erupted to ~FL200 • Emissions continued over several days • Useful case to look at • Full range of satellite imagery • Area largely cloud free • Use NAME to simulate first 10 days of emissions • Continuous release from surface to FL200 • Compare concentrations (FL100 & FL200) with satellite imagery, particularly ch4-ch5

  12. Etna 28/10/2002

  13. Etna 29/10/2002

  14. Etna 30/10/2002

  15. Etna 31/10/2002

  16. Etna 29/10/2002 Coloured by height(yellow=low level, red = high level)

  17. Effect of poorly resolved volcano Model Actual Inversion Peak not resolved Inversion above ‘model’ summit Plume also in boundary layer Inversion below summit Plume remains in free troposphere

  18. Poorly resolved orography • Particular problem with isolated peaks • No simple solution as NWP data will not properly represent flow around/over peak • If use ‘model’ summit height column is ‘stretched’ - material spreads over twice the height, giving lower concentrations • Suggest using ‘elevated’ source

  19. Impact of poorly resolved orography Release surface to FL200 Release FL100 to FL200

  20. Future Work • Volcanic ash detection • SEVERI on MSG (including AVHRR ch4-ch5) • 15 minute imagery • Automatic detection system (Helen Watkin’s talk) • Upgrade to MSG • Operational implementation • Modelling • Need better definition of ‘Visual Ash Cloud’ - more appropriate would be ’concentrations hazardous to aviation’ • Include sulphur as well as ash • Ensemble approach - multiple NAME runs on ECMWF EPS members (51)

  21. Summary • Volcanic ash detection system and NAME predictions give increased confidence in operational VAAC results • Etna case study demonstrates the value of these tools • Issues for future work include • calibration of satellite imagery • representation of orography / height of release • definition of hazardous ash concentrations

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