2. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Modelling and Forecasting of the Eyjafjallajökull eruption Anton Muscat Met Office

3. © Crown copyright Met Office

4. Order of presentation: UK Met Office and London VAAC Creating a weather forecast NAME – the Met Office’s dispersion model Responsibilities of a VAAC Volcanic eruption – typical timeline Using observations to verify NAME Conclusions

5. © Crown copyright Met Office Met Office and London VAAC Met Office provides weather and climate services to UK Government, General Public and commercial customers. Many of the forecasts are produced from the forecasting Operations Centre at Exeter. London VAAC (Volcanic Ash Advisory Centre) is actually based in the Operations Centre at Exeter and is part of a forecasting team who provide advice on many different aspects of atmospheric dispersion (nuclear accidents, chemical release, biological release, etc.)

6. © Crown copyright Met Office du = ∂p – fv dt ∂x dv = ∂p + fu dt ∂y p = RT ρ Risk Analysis & Communication Knowledge 70 levels 25km 65km high Creating the weather forecast Forecast Model Observations Application of classical laboratory physics to the thin shell of turbulent gases that is our atmosphere

7. © Crown copyright Met Office From weather forecast to predicting plume movement Weather forecast will provide us with details of how air is moving within the atmosphere Apply this weather forecast (wind and other information) to a dedicated Dispersion Model Met Office have a dispersion model called NAME (Numerical Atmospheric dispersion Modelling Environment III) NAME was developed following the Chernobyl accident in 1986 and is a world-leading dispersion model.

8. © Crown copyright Met Office Applications of NAME Nuclear and chemical releases Volcanic ash Disease spread (foot and mouth, blue tongue disease, legionaires disease) Major fires Emergency planning – ‘what if’ scenarios

9. © Crown copyright Met Office Dispersion modelling Volcano Wind transports the ash Random wind variations spread ash into a broad plume Gravity causes ash to fall through the atmosphere Rain washes ash on to the ground

10. © Crown copyright Met Office NAME – State of the Art system NAME calculates dispersion by tracking ash particles through a simulated atmosphere (Lagrangian particle modelling). Modelled ash particles have variable size and mass. Particles are moved by the three dimensional forecast winds that vary in time through the forecast. Particles’ motion also has a random component to represent the effects of atmospheric turbulence. Particles are removed from the atmosphere by several physical processes: fall out due to gravity - sedimentation settling on the surface – dry deposition washout where the pollutant is 'swept out' by precipitation rainout where the pollutant is absorbed directly into cloud droplets

11. © Crown copyright Met Office A re-cap of the process © Crown copyright Met Office First – observe the volcanic ash at source How high? How dense? Next – Forecast the weather patterns Horizontal and vertical winds Combine the two in a well proven dispersion model

12. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY VAAC - Volcanic Ash Advisory Centres 9 VAACs implemented by ICAO in 1987

13. © Crown copyright Met Office London VAAC The VAAC London procedures are set up to ensure absolute reliability in a safety critical situation VAAC London is staffed 24x7 with forecasters trained to identify ash in satellite imagery, to operate the NAME dispersion model, and to generate the standard advisory charts Once an event is in progress, expert scientists are on call to support the 24x7 operation

14. © Crown copyright Met Office Role of VAACs International Civil Aviation Organisation (ICAO) recommends VAACs should provide guidance on presence of “any ash” in the atmosphere (London VAAC uses > 2x10-4 g/m3) Production of advisories detailing the spatial dispersion of VA Running (and/or utilisation of output from) NWP dispersion models Monitoring of observational data, especially satellite imagery for the presence of VA VAAC advisories and graphics are produced out to 24 hours for use by state Met Watch Office (MWO) MWO produce VA SIGMETs based on VA Advisories

15. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Standard VAAC Graphic

16. © Crown copyright Met Office Moving from ash presence to ash concentration Original international VAAC guidance of no-ash zone based on empirical evidence of the edge of plume. Estimated volcano release rates for Eyjafjallajökull indicated that no-ash limit equated to peak concentrations of 200 micrograms/m3 (red zone), corroborated by observations. Consultation based on safe engine ingestion rates indicated that concentrations 10 times higher could be hazardous. Black zone introduced to indicate peak concentrations of 2000 micrograms/m3 and higher.

17. © Crown copyright Met Office Supplementary London VAAC Products During the event CAA asked London VAAC to provide supplementary products to standard service Red and black charts Red and black charts with black buffer zone Red, grey and black charts CSV files for red, grey and black thresholds 3 hourly update charts 5,000ft layer charts 5 day red, grey and black charts London VAAC has no influence on these thresholds. They are stipulated by CAA on advice from engine manufacturers

18. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Supplementary Red, Grey and Black Chart

19. © Crown copyright Met Office

20. Volcanic eruption – a typical timeline UK Met Office has close links with Iceland Met Office (IMO) – VA exercises every 3 months. In the event of increased seismic activity on (or near) Iceland, IMO contact Met Office to inform. The moment an eruption occurs (or is thought likely to occur soon) IMO contact Met Office Assuming that an eruption has started, NAME is run with the supplied details (height of plume, etc.) Typically, VAG/VAA guidance is issued approx. 60-90 minutes after eruption starts. VAG/VAA guidance then updated regularly thereafter, AT LEAST every 6 hours. London VAAC forecasters take part in regular teleconferences with Eurocontrol/NATS, as well as liaising with VAAC Toulouse and VAAC Montreal.

21. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Forecasting Process NAME Dispersion Model Meteorology Volcanology: Mass, height, particle sizes

22. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Differences between ash dispersion models Driving Meteorology Quality – resolution, accuracy, frequency of updates…. Variables used - wind, precipitation, temperature… Dispersion Model Differences Processes for removing ash – sedimentation, wet & dry deposition Retention of old ash Volcano characteristics Height, diameter and time variance of eruptive column Ash release rate Ash particle size and density

23. © Crown copyright Met Office Techniques for observing Volcanic Ash Satellite imagery LIDAR (Light Detection and Ranging) Sampling of atmosphere by suitably equipped aircraft. Reports from aircraft when they encounter ash. Reports of ash depositing on the ground

24. © Crown copyright Met Office Satellite imagery Okay in certain circumstances (newly erupted ash, clear skies) but increasingly difficult to see ash after approx. 24 hours in the atmosphere, and impossible to detect when cloud overlays the ash. Animations of satellite imagery, over a period of time, are the best way to observe ash via satellite imagery.

25. © Crown copyright Met Office Satellite imagery – contd: Satellite images can show ash in some circumstances: when the ash is very dense and when it is high in the atmosphere Unlike smoke it is not easy to see in the standard visible or infrared wavelengths However, the silica in the ash has specific radiative properties that can be used to make it visible in some of the more advanced satellite instruments now in use It is also possible to detect the sulphurous gases associated with the eruption in the same way. Unfortunately, away from the volcano, the two do not always stay together.

26. © Crown copyright Met Office Satellite animation The following shows a satellite animation over approx. 5 days (5 th -11 th May 2010) using 3-hrly satellite images. Using a viewing channel called Dust RGB which provides a false-colour satellite image Note that volcanic ash is clearly visible close to Iceland but becomes increasingly diffuse with time.

27. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Satellite Ash Retrievals Exploiting the different absorbing, emitting and scattering properties of water, ice and ash at different wavelengths

28. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY

72. Comparison with NAME 1200 UTC 10/05/2010 Edge of ‘visible’ plume on satellite retrievals

73. Comparison with other models: 1200z on 10 May PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY

74. © Crown copyright Met Office Light Detection and Ranging (LIDAR) Emits a pulse of laser light and detects backscatter signal Detects the altitude and thickness of aerosol layers When collocated with other technology is possible to estimate the total aerosol content of the atmosphere and mass concentration Only available in a limited number of fixed locations.

75. © Crown copyright Met Office LIDAR locations in the UK

76. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY NAME vs LIDAR observations: Exeter Arrives about 12 hours early

77. © Crown copyright Met Office Suitably equipped aircraft Provides high-quality data Often not in real-time – data can be many hours old before it is viewable by forecasters Expensive to operate Limited coverage

78. © Crown copyright Met Office Satellite imagery comparison with NAME 1200 UTC 10/05/2010 Edge of ‘visible’ plume on satellite

79. © Crown copyright Met Office Other observations During the ash event, many ad-hoc observations of volcanic ash were received Some could be verified, some could not London VAAC considered these observations when compiling the VAG/VAA products Changes were made to the computer model output if evidence from Satellite/LIDAR/Observations warranted it.

80. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Emission Characteristics are Biggest Source of Uncertainty Current releases: Eruption plume: Possible solutions: Weighted Gaussian Probabilistic

81. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Carrying old ash is important for Eyjafjallajökull 1 2 3 4 5 Age of ash (days): 10 May

82. © Crown copyright Met Office Concluding remarks On vast majority of occasions, NAME successfully captured horizontal extent of the ash plume and the variations within it, including indications of peak concentrations. As with all models, concentrations are determined by the characteristics of the volcanic emission – mass, particle size and height – which are hugely uncertain. Recognize a need for a consistent approach by all VAACs to forecasting VA – this is currently being taken forward.

83. © Crown copyright Met Office Future Plans Forecasting capability/flexibility to provide products tailored to any requirements Continued quantitative assessment of ash forecasts against observations and development of implementation plans for improved monitoring systems Real time calibration of volcanic source term based on observations More frequent forecast products with more vertical resolution, giving improved temporal and spatial granularity Extension to provide forecasts of SO2 and related pollutants. Development of products which sample uncertainty in the volcanology and meteorology to enable better-informed risk assessments

84. © Crown copyright Met Office Any Questions?

85. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Observational Verification Doug Johnson Met Office

86. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Ash observed from 3000m descending to 1200m in afternoon of 16 th April. Mass concentration estimated as ~ 750  gm -3 or ~250-2300  gm -3 Case 1: Onset of Plume 16 th April Cloud Ash: descending and mixing into boundary layer Exeter Ash Cardington Ash observed from 3000m descending to 1500m in morning of 16 th April. Mass concentration estimated as ~ 330  gm -3 or ~100-1000  gm -3

87. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY FAAM BAe 146 research aircraft

88. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Case 2: Irish Sea Event (4 th May 2010) 06:00UTC

89. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY 12:00UTC Case 2: Irish Sea Event (4th May 2010)

90. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY 18:00UTC Case 2: Irish Sea Event (4th May 2010)

91. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY 4 th May: Slicing the lidar along the track of the BAe146 aircraft. Note the high aerosol mass over Wales and Irish Sea below 22,000ft

92. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Satellite imagery supports the model, but difficult to interpret because of the presence of cloud Ash

93. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Ash Satellite imagery supports the model, but difficult to interpret because of the presence of cloud

94. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Satellite imagery supports the model, but difficult to interpret because of the presence of cloud Ash

95. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Results from Aberystwyth lidar 10:02UTC Not much here

96. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Results from Aberystwyth lidar 10:44UTC Increasing

97. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Results from Aberystwyth lidar 11:00UTC Increasing

98. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Results from Aberystwyth lidar 11:48UTC Increasing AOD=∫ke * conc * dz AOD=0.35 dz = 3000m k e = 0.6m 2 g -1 Conc= 190  gm -3 = 70-600  gm-3

99. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Lidar scan 13:20 – 13:50 Nephelometer Profile back out of the layer 13:42-13:48 Lidar profile at 13:45 Depolarization Extinction Dropped into ash layer then aborted owing to SO2 conc Ash (Angstrom exponent) H 2 SO 4

100. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Lidar scans 14:30 – 15:00 Ash Range corrected signal Depolarisation ratio H 2 SO 4 Ash H 2 SO 4 (invisible) H 2 SO 4 H 2 SO 4 (invisible)

101. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Conclusions from 4 th May case Forecast position and detail of plume very good although the satellite data is difficult to interpret. ‘Red zone’ implies 200-2000  gm -3. Lidar suggests ~ 70-600  gm -3. Agreement between the NAME model and the observations is acceptable.

102. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY 950 hPa wind and height 500 hPa wind and height Vertical Structure of the Ash Plume 10 May 1200z

103. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Vertical Structure: FL000-FL200 for 12Z 10 May FL000-FL050 FL100-FL150 FL050-FL100 FL150-FL200 10 -17 10 -16 10 -15 10 -14 10 -13 10 -12 Normalised ICAO ash concentrations

104. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY FL200-FL250FL250-FL300 FL300-FL350 Vertical Structure: FL200-FL350 for 12Z 10 May 10 -17 10 -16 10 -15 10 -14 10 -13 10 -12 Normalised ICAO ash concentrations NB: Scaling to peak concentrations in thinner layers depends on source strength and height.

105. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Volcanic emissions – ash and SO 2 (current) Prototype ash (brown) and SO2 (colours) retrievals using multi-spectral channels on Seviri Montserrat hourly images Note SO2 rises higher than ash and is differentially advected by stronger winds aloft

106. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Is the ash visible to the naked eye? Visibility depends on the viewing angle Radiative transfer calculations using typical optical properties of the ash suggest that: 1000m layer of 2000 micrograms per cubic metre is semi- transparent looking directly up or down; Opaque from very oblique viewing angles.

107. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Future Plans Forecasting capability has flexibility to provide products tailored to any requirements Continued quantitative assessment of ash forecasts against observations and development of implementation plans for improved monitoring systems Real time calibration of volcanic source term based on observations More frequent forecast products with more vertical resolution, giving improved temporal and spatial granularity Extension to provide forecasts of SO2 and related pollutants. Development of products which sample uncertainty in the volcanology and meteorology to enable better-informed risk assessments

108. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY Met Office Objective To Be Recognised As the Best Weather And Climate Service In the World

109. © Crown copyright Met Office PRESENTATION DELIVERED WITH EXPERT COMMENTARY. PLEASE CHECK AGAINST DELIVERY NAME – Chernobyl simulation NAME tracks ‘particles’ through the flow Each particle responds to the local flow and turbulence (represented by systematic and random aspects of the motion) Uses flow information from the UM