1. Discrepancies Between Satellite Detection and Forecast Model Results of Ash Cloud Transport: Case Study of the 2001 Eruption of Mt. Cleveland Volcano, Alaska David Schneider, USGS-Alaska Volcano Observatory Rene Servranckx, Environment Canada, Montreal VAAC Jeff Osiensky, National Weather Service, Anchorage VAAC

2. Motivation/Background The understanding that total avoidance of ash clouds is required but confusion about what is meant by (or how to achieve) “zero tolerance”. A realization that operational decisions typically involve resolving conflicts between data sources. How should warnings and info releases utilize model results, satellite data, and observer reports? What is the proper “weight” to give each when they are in conflict? The question of how long to keep a warning going A look at the 1991 eruption of Cleveland volcano will illustrate these issues, but not answer any of these questions.

3. Location Map R. Wessels Cleveland Volcano Anchorage About 900 miles from Anchorage; 5675 ft high. Eruption in 2001 is the largest from a seismically unmonitored volcano since the formation of AVO in 1988.

4. Summary of February 19 Eruption Eruption detected in AVHHR satellite image as part of routine monitoring by an AVO remote sensing analyst, about 3 hours after the eruption start. Ash production for about 6 hours, and detected in GOES satellite images for 48 hours. No Color Code issued by AVO for Cleveland because of the lack of a seismic monitoring network (policy since changed). Combined response of 3 VAACS (Anchorage, Washington, and Montreal), Anchorage Center Weather, and the AVO. Pointed out a need for additional tools to facilitate collaboration (VACT).

5. VAAC Map

6. Ash Cloud Forecast Models A number of models used by responding groups PUFF: Anchorage VAAC and AVO Canerm: Montreal VAAC Vaftad: Washington VAAC Although there are differences between the models, they are typically in general agreement. Ash particles are essentially tracers of flow in the atmosphere, and output is influenced by a number of factors. The ash is predicted, not detected.

7. Satellite-based Ash Cloud Detection AVHRR Band 4 -60 Degrees C 50 AVHRR Band 4m5 -5 Degrees C 5 Split-window method is a common technique: Brightness temperature difference (BTD) between 2 thermal infrared channels Semitransparent volcanic clouds generally have negative BTDs while meteorological clouds generally have positive BTDS

8. Satellite-based Ash Detection The magnitude of the BTD signal depends upon many factors: –Cloud opacity (amounts of ash and water in the cloud) –Size and size distribution of the cloud particles –Temperature contrast between the cloud and the surface beneath it –Satellite viewing angle –Atmospheric conditions Thus, the detection limit varies (+/-) between eruptions and during cloud transport.

9. AVHRR Band 3: 2/19/01 1645 UTC Thermal Anomaly -5550Degrees C Cold Cloud

10. AVHRR Band 3: 2/19/01 1645 UTC

11. AVHRR Band 4m5: 2/19/01 1645 UTC -55Degrees C 50 nmi (100 km)

12. AVHRR Band 4: 2/19/01 1645 UTC -5510Degrees C -53.5 C - 33 C

13. 1600 UTC: 2/19/01 E + 1 hour

14. 1800 UTC: 2/19/01 E + 3 hours

15. 2000 UTC: 2/19/01 E + 5 hours

16. 2200 UTC: 2/19/01 E + 7 hours

17. 0000 UTC: 2/20/01 E + 9 hours

18. 0200 UTC: 2/20/01 E +11 hours

19. AVHRR Band 4m5: 2/19/01 1645 UTC -55Degrees C Upper Level Cloud >FL300 Lower Level Cloud <FL200

20. 1800 UTC: 2/19/01 E + 3 hours GOES Band 4m5 -5 Degrees C 4

21. FL S-200FL 200-350 1800 UTC: 2/19/01 E + 3 hours

22. 2000 UTC: 2/19/01 E + 5 hours GOES Band 4m5 -5 Degrees C 4 SIGMET Covers this area at 2 levels Supported by PIREP Upper Level Cloud Appears in BTD Images

23. 2200 UTC: 2/19/01 E + 7 hours GOES Band 4m5 -5 Degrees C 4 Lower Level Cloud Starts to “Fade” in BTD Images

24. 0000 UTC: 2/20/01 E + 9 hours GOES Band 4m5 -5 Degrees C 4

25. FL S-200 0000 UTC: 2/20/01 E + 9 hours FL 200-350

26. 0200 UTC: 2/20/01 E +11 hours GOES Band 4m5 -5 Degrees C 4 FL360: “Ash and sulfur odor in cockpit” FL360: “Cinders and sulfur odor in cockpit”

27. 0200 UTC: 2/20/01 E +11 hours GOES Band 4m5 -5 Degrees C 4 SIGMET extended to cover cloud <FL400

28. 0400 UTC: 2/20/01 E +13 hours GOES Band 4m5 -5 Degrees C 4

29. 0600 UTC: 2/20/01 E +15 hours GOES Band 4m5 -5 Degrees C 4 SIGMET “uses” more model guidance

30. FL S-200 0600 UTC: 2/20/01 E + 15 hours FL S-200FL 200-350

31. 0800 UTC: 2/20/01 E +17 hours GOES Band 4m5 -5 Degrees C 4

32. 1000 UTC: 2/20/01 E + 19 hours GOES Band 4m5 -5 Degrees C 4

33. 1200 UTC: 2/20/01 E + 21 hours GOES Band 4m5 -5 Degrees C 4

34. FL S-200 1200 UTC: 2/20/01 E + 21 hours FL 200-350

35. 1400 UTC: 2/20/01 E + 23 hours GOES Band 4m5 -5 Degrees C 4

36. 1600 UTC: 2/20/01 E + 25 hours GOES Band 4m5 -5 Degrees C 4

37. 1800 UTC: 2/20/01 E + 27 hours GOES Band 4m5 -5 Degrees C 4 As signal starts to fade, the SIGMETs give satellite images more “weight”.

38. FL S-200 1800 UTC: 2/20/01 E + 27 hours FL 200-350

39. 2000 UTC: 2/20/01 E + 29 hours GOES Band 4m5 -5 Degrees C 4

40. 2200 UTC: 2/20/01 E + 31 hours GOES Band 4m5 -5 Degrees C 4

41. 0000 UTC: 2/21/01 E + 33 hours GOES Band 4m5 -5 Degrees C 4

42. FL S-200 0000 UTC: 2/21/01 E + 33 hours FL 200-350

43. 0200 UTC: 2/21/01 E +35 hours GOES Band 4m5 -5 Degrees C 4

44. 0400 UTC: 2/21/01 E +37 hours GOES Band 4m5 -5 Degrees C 4

45. 0600 UTC: 2/21/01 E +39 hours GOES Band 4m5 -5 Degrees C 4

46. FL S-200 0600 UTC: 2/21/01 E +39 hours FL 200-350

47. 0800 UTC: 2/21/01 E +41 hours GOES Band 4m5 -5 Degrees C 4

48. 1000 UTC: 2/21/01 E +43 hours GOES Band 4m5 -5 Degrees C 4

49. 1200 UTC: 2/21/01 E +45 hours GOES Band 4m5 -5 Degrees C 4

50. FL S-200 1200 UTC: 2/21/01 E +45 hours FL 200-350

51. 1400 UTC: 2/21/01 E +47 hours GOES Band 4m5 -5 Degrees C 4

52. 1600 UTC: 2/21/01 E +49 hours GOES Band 4m5 -5 Degrees C 4 SIGMET HOTEL 12 cancelled at 1715 UTC on 2/21/01

53. 1800 UTC: 2/21/01 E + 51 hours FL S-200FL 200-350

54. 0000 UTC: 2/22/01 E + 57 hours FL S-200FL 200-350

55. 0600 UTC: 2/22/01 E + 63 hours FL S-200FL 200-350

56. 1200 UTC: 2/22/01 E + 69 hours FL S-200FL 200-350 2/22/01 at 1408 UTC FL360: “Particles and strong odor in cockpit”

57. 1800 UTC: 2/22/01 E + 75 hours FL S-200FL 200-350

58. Final Thoughts With satellite images, does an absence of detectable ash mean that ash is absent? Does the prediction of ash in a dispersion model mean that ash is present? The eruption response demonstrates how the balance between data sets can evolve. Cloud height is crucial but hard to determine. No reports of damage to aircraft. Does this mean that no damage occurred? Was the decision to end warnings after 48 hours prudent given a report of odor 24 hours later? (Zero tolerance?)

59. Thank You

60. Composite Ash Movement Image by K. Papp

61. 1800 UTC: 2/19/01 E + 3 hours FL S-200FL 200-350

62. 0000 UTC: 2/20/01 E + 9 hours FL S-200FL 200-350

63. 0600 UTC: 2/20/01 E + 15 hours FL S-200FL 200-350

64. 1200 UTC: 2/20/01 E + 21 hours FL S-200 FL 200-350

65. 1800 UTC: 2/20/01 E + 27 hours FL 200-350FL S-200

66. 0000 UTC: 2/21/01 E + 33 hours FL S-200FL 200-350

67. 0600 UTC: 2/21/01 E +39 hours FL S-200FL 200-350

68. 1200 UTC: 2/21/01 E +45 hours FL S-200FL 200-350 Last GOES detection was at 1600 UTC on 2/21/01.

69. 1600 UTC: 2/19/01 E + 1 hour GOES Band 4m5 -5 Degrees C 4