1. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Modeling Volcanic Ash Transport and Dispersion: Expectations and Reality René Servranckx & Peter Chen Montréal Volcanic Ash Centre Canadian Meteorological Centre

2. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Presentation Topics: Ash Transport Models u Reality 20 years from now u Expectations for Ash Transport Models (TM) u Reality today / Limiting factors u Areas for improvement

3. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada June 22, 2024

4. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada June 22, 2024

5. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada June 22, 2004!

6. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada ACCURATE guidance on SPACE / TIME LOCATION / 3D STRUCTURE of airborne ash LITTLE (or no) UNCERTAINTY (ash / no ash) TIMELY delivery Implications for TM? What area aviation users TM expectations?

7. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Components: Ash Modeling Problem Accuracy and timeliness of TM guidance depends on: Volcanic Ash Source (‘’Source Term’’ / eruption parameters) Meteorology Transport and Dispersion (TM)

8. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Despite uncertainties, TM: Are of great value! Especially important for REAL-TIME, operational response Sometimes, the ONLY guidance available Must be used in conjunction with other tools (remote sensing, etc.) Can not be used blindly!

9. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Limiting Factors : VOLCANIC ASH SOURCE Eruption parameters largely unknown / poorly quantified Detection of eruptions / airborne ash is problematic Poor quantitative estimates of atmospheric ash loading / only 2D  3D is needed for TM Threshold ash concentrations that pose threat to ‘’aviation’’ (?)  May be very small (NASA DC-8 Hekla incident) ‘’Visual Ash Cloud’’ criterion on TM guidance is subjective DEFAULT SCENARIOS and LOW THRESHOLD values in TM guidance

10. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Limiting Factors : METEOROLOGY HORIZONTAL and VERTICAL resolution of Numerical Weather Prediction (NWP) Models Vertical coordinates are not Flight Levels ‘’standard atmosphere’’ Representation of earth’s surface (topography) in NWP models Mt Mckinley, AK 6194 m 2640 m Incomplete knowledge of initial conditions of the atmosphere Predictability of atmosphere / Accuracy of NWP vary with flows / patterns

11. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Limiting Factors : TRANSPORT / DISPERSION VOLCANIC ASH SOURCE component METEOROLOGY component Parameterization of dispersal, removal and deposition of ash Real time assimilation of airborne ash is not done Predictive ability varies with atmospheric conditions

12. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Areas for improvement: VOLCANIC ASH SOURCE COMPONENT 1998 and 2003 WMO / ICAO volcanic ash meetings: ‘’Substantial improvements could be made in TM guidance if source term estimates were improved’’ ICAO (IAVW Ops Group) to IAVCEI: QUANTITATIVE estimates of eruption parameters for TM? NASA DC-8 encounter with Hekla diffuse plume: damage from very small ash concentrations (?)

13. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Areas for improvement: VOLCANIC ASH SOURCE COMPONENT If unconditional ash-avoidance is the rule, small concentrations must be accurately predicted  Good estimate of Source term is important! Remote sensing: Any technological advancement that might improve quantitative estimates of the 3D distribution of airborne ash Assimilation of volcanic ash data in TM : Exploratory work has been done (Siebert et al. 2002; NOAA Air Resources Laboratory) How much can we achieve?  Highly dependent on remote sensing improvements (quantitative 3D distribution)

14. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Areas for improvement: METEOROLOGY and DISPERSION / TRANSPORT Components Improvements to NWP Models are ongoing Improvements to TM also ongoing ENSEMBLE FORECASTING: Already done for NWP Models; applicable to TM Many runs (single or multiple models) using slightly different initial conditions BASIC IDEA: AVERAGE of many runs BETTER than single run Spread among runs is gives an estimate of uncertainty

15. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Example: ‘’Visual ash clouds’’ from 4 TM runs valid at same time

16. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Finagle’s Laws of Information The information you have is not what you want The information you want is not what you need The information you need is not what you can obtain The information you can obtain costs more that you want to pay

17. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Corollaries What you ‘’see’’ / interpretation depend on : Tools / Technology How information is presented How one looks at information What you ‘’see’’ may not be what you get !

18. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada

19. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada

20. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada

21. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Impact of changing ‘’visual ash cloud’’ value ALL IMAGES TO FOLLOW ARE FROM SAME TRANSPORT MODEL RUN WITH SAME SOURCE TERM CONDITIONS 1 hour eruption of Cleveland starting 15 UTC 19 Feb 2001 Images valid 45 hours after start of eruption CANERM (TM) diagnostic average ash concentration in FL200 - FL350 (micrograms per cubic meter)  perception of where ash is or is not present!

22. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada 200 10080 50 101

23. Environment Canada Meteorological Service of Canada Environnement Canada Service météorologique du Canada Summary Transport Models: u Expectations are high u Despite uncertainties, VALUABLE! u Must be used with other sources of information u Can not be used blindly /require careful interpretation / knowledge of uncertainties u New ways of looking at information and estimating uncertainties (Ensemble forecasts) u Accuracy can be increased by reducing uncertainties What can we do to bridge the gaps?