Volcanic Sulphur Dioxide

Volcanic Sulphur Dioxide

Overview Background & context Claire Witham VAAC SO 2 forecast demonstration Dov Bensimon Rolls Royce work on SO2 Rory Clarkson New capabilities to remotely sense SO2 - Marcel Roux

Background & Context

Global Volcanic Emissions of SO2 Great animated graphic by Simon Carn showing global emissions : https://twitter.com/simoncarn/status/951526193270087683/photo/1

Volcanic emissions of SO2 Significant annual emissions Gas but no ash Separation from ash Long range transport Long duration emissions from effusive eruptions

Aircraft encounters with SO2 Encounters of commercial aircraft with volcanic gas plumes have been reported since the 1980s. In the 2008 database of aviation encounters with volcanic ash, there are at least 15 incidents between 1980 and 2008 that directly report encounters with sulphur dioxide, many in the form of detection of sulphurous smells in the cabin. The 2008 eruption of Kasatochi is particularly striking due to the number of gas encounters reported as the plume moved over Canada and the northern USA. On 11 August 2008, dozens of pilots reported sulphurous odours in the cockpit

SO2 interest from ICAO The first job card for sulphur dioxide was issued on 22 March 2013. In response to request, the VASAG produced a paper on volcanic SO2 for the second meeting of the METP (Montréal, 17-21 October 2016). This meeting endorsed changes that put the focus on identifying and quantifying health risks to aircraft occupants from sulphur dioxide. The third meeting of the WG-MISD Volcanic Ash and Sulphur Dioxide (VASD) Work Stream (Tokyo, 14 June 2017) reviewed the job card and proposed that other impacts on the aircraft arising from exposure to sulphur dioxide, such as economic and efficiency impacts should be added to the job card.

VAAC SO 2 forecast demonstration Presented by Dov Bensimon VAAC Montreal 8

Proof of concept This presentation is meant to illustrate what can be done by a Volcanic Ash Advisory Centre (VAAC) to forecast the displacement of sulphur dioxide (SO 2 ) given an observation. The methodology presented here is a qualitative example and by no means a finalized or unique procedure to be followed. 9

Email notification received VAAC Montreal receives real-time notifications of SO 2 such as the one below from the Support to Aviation Control Service. 10

Detection of SO 2 This is an example of a real-time detection of SO 2 received on 1 October 2018. The email was received at 0404 UTC for a detection at 0220 UTC. The height of the SO 2 plume is indicated by coloured pixels in kilometers on this image. 11

Tracking Sulphur Dioxide Looking at the location of the detection and which volcanic ash advisories are current at the time of the detection, it is presumed that this SO 2 came from Sabancaya. It would also be possible to model the evolution to either: confirm which volcano it came from (backwards in time) see where the area of SO 2 will go in the coming hours (forward in time) 12

Define a point to launch the model The latitude and longitude provided in the notification from SACS is used to define a point that is used to launch the Atmospheric Transport and dispersion Model. Alternatively, it would also be possible to define a polygon from which to start a simulation of the ATM. The polygon would have to be approximated from the SACS data. 13

Simulation parameters The simulation that was launched for this example assumed a release in a cylinder extending from the surface to a height of 9 km above ground level (AGL). This was the value provided in the SACS notification for the SO 2 detection. Since this was an instantaneous detection, this was modelled as a short release (30 minutes). These are all adjustable parameters, so they can be modified if judged necessary. Darkened area represents dispersion model output grid. 14

Performing a simulation In this case, a simulation using the Canadian Meteorological Centre's Lagrangian transport and dispersion model, MLDP, was performed. The simulation was run over a period of 24 hours, with a release of a million Lagrangian particles in 30 minutes, in a column from the surface to a height of 9 km AGL. The output grid (shown on the previous slide) on which the concentrations were calculated had 722 grid points in each the x and y directions, and a spacing of 33 km between points. The simulation was completed in 5 minutes on CMC's supercomputer. 15

Raw model output One has to decide which output variable from the model and which vertical layer in the atmosphere to display. Below is an example of raw model output. It shows a 14- hour forward forecast of concentrations between the surface and 9 km AGL. 16

Calibration of model output The calibration of model output is the key step in this process. "Calibration" means deciding which of the raw model output values is chosen to depict an area of SO 2 in the final product to be delivered to clients. Another observation of SO 2 is needed in order to choose which contour of the model output is displayed in the final product. This same process is true when forecasting volcanic ash. 17

Second observation of SO2 This is an example of a real-time detection of SO 2 plume height received on 1 October 2018. The email was received at 1523 UTC for a detection at 1329 UTC. 18

Second observation of SO2 This is an example of a real-time detection of SO 2 concentration in Dobson Units (DU) received on 1 October 2018. The email was received at 1523 UTC for a detection at 1329 UTC. 19

Calibrated model output Using the areal extent in the second observation of SO 2, one tries to find the threshold of SO 2 in the model output that best fits this observation. The example below is the same model output shown in a previous slide, i.e. a 14-hour forward forecast of concentrations between the surface and 9 km. 20

Calibrated model output Once the model output has been calibrated, it is possible to use it to anticipate where SO 2 will go in the future. This process of calibration can be repeated with each subsequent observation in order to refine the forecast zone of SO 2. 21

Conclusion It is hoped that this demonstrations spurs discussion as to a possible path forward for forecasting SO 2. Comments and questions are welcome! 22

Rolls Royce Work on SO2

New capabilities to remotely sense SO2 Presented by Marcel Roux VAAC Wellington 24

FROM MATERIAL PRESENTED AT VAAC BP SESSION OLD VS NEXT GENERATION SATELLITE IMAGERY INTERCOMPARISON AOBA eruption 26 and 27 July 2018 Absence of meteorological cloud allowed clear tracking of various ash and SO2 areas using Himawari satellite data Fiji Airways assisted VAAC with cross checking a spurious report evening of 27 th. Resulted in the VAAC forecaster only considering Fiji Airways reports as observations that could result in change to plume base and tops.

Image placeholder Aoba eruption 10-11 April 2018 Ash RGB