Several issues on VAAC operation - Tokyo VAAC s approach -

Transcription

1 Several issues on VAAC operation - Tokyo VAAC s approach - SATOSHI HARADA VAAC TOKYO / JMA

2 Several issues on VAAC operation 1. How to deal with information overload? 2. How to use inconsistent plume height reports? 3. How to reconcile model output and observation? 4. How to decide cessation of advisory?

3 Several issues on VAAC operation 1. How to deal with information overload? 2. How to use inconsistent plume height reports? 3. How to reconcile model output and observation? 4. How to decide cessation of advisory?

4 How to deal with information overload? (1) Tokyo VAAC receives eruption reports from VOs relatively more than other VAACs. In Japan, almost every puff is reported as an eruption. Every significant eruption reported by KVERT and SVERT Mt. Sakurajima (South of Japan) makes puffs (minor eruptions) 6 times a day on average.

5 How to deal with information overload? (2) Necessity to avoid too many SIGMETs Too many issuance may induce cry wolf syndrome. ASHTAM could be the appropriate message to convey information about weak volcanic activity. (see paragraph of IAVWOPSG/5 report) Tokyo VAAC does not take ASHTAM approach Sakurajima erupts intermittently rather than continuously.

6 How to deal with information overload? (3) Tokyo s approach to minimize number of VAAs VAA is not issued for eruptions whose ash height does not exceed maximum height in last 3 hours. e.g. Sakurajima (Japan) in January eruptions reported 114 VAAs issued (3.7 times/day) 0000Z FL Z FL Z FL Z FL Z FL080 VAA issued VAA NOT issued

7 How to deal with information overload? (4) When weak eruptions continue like at Sakurajima..., How many advisories/warnings are appropriate, from user s point of view? Who should control it? VO, VAAC or MWO? Should volcano observatories control number of reports? Should VAACs reduce number of VAAs, so that MWOs can issue SIGMET for really significant one? Should MWOs issue SIGMETs only for selected VAAs? Who is responsible of taking ASHTAM approach?

8 Several issues on VAAC operation 1. How to deal with information overload? 2. How to use inconsistent plume height reports? 3. How to reconcile model output and observation? 4. How to decide cessation of advisory?

9 How to use inconsistent plume height reports? (1) Plume Height is the most crucial source parameter. The amount of ash highly depends on ash column height. The higher, the more safety risk on aircraft operations. Height estimated by various sources. Ground observation Live view, Lider, Radar, Seismometer Pilot reports Satellite Tokyo VAAC takes highest value, from the safety point of view (NOT prioritizing information sources).

10 How to use inconsistent plume height reports? (2) Plume heights tend to be inconsistent. Which one should be selected? Should we put priorities among them? What if only unreliable value is available? How can we deliver uncertainty of the value?

11 Several issues on VAAC operation 1. How to deal with information overload? 2. How to use inconsistent plume height reports? 3. How to reconcile model output and observation? 4. How to decide cessation of advisory?

12 How to reconcile model output and observation? (1) Model output is not always coincide with observed ash boundaries. So, to adjust the initial condition of ash dispersion, some VAACs run their models again from the origin with different source parameters.

13 How to reconcile model output and observation? (2) Tokyo VAAC s unique approach. Initial ash particles: use observed ash boundaries Disperse particles from observation time (not from the origin) forecast from T+0 T+0 T+6 T+12 forecast from T+6 T+18 forecast from T+12 Observation at T+6 Observation at T+12 Observation at T+18

14 How to reconcile model output and observation? (3) Advantage Do not have to go back to the origin Do not have to adjust model output to fit into observation data Able to forecast as long as ash clouds are observed Disadvantage Inconsistent with past VA dispersion forecast Observed VA boundaries may also contain certain uncertainty Observation may not always be successful Model output instead of observed ash boundary may be applicable

15 Several issues on VAAC operation 1. How to deal with information overload? 2. How to use inconsistent plume height reports? 3. How to reconcile model output and observation? 4. How to decide cessation of advisory?

16 How to decide cessation of advisory? (1) Ash in the model will not be dissipated easily. Some VAACs take gradual cessation approach c.f. paragraph i) in IAVW Handbook

17 How to decide cessation of advisory? (2) When VA cloud come to disappear on Satellite images..., Should necessarily VAA remain for more 12 or 18 hours? How to judge when is the cessation time of the VAA? It is worth to share a policy for judgment of cessation.