1. Weather Radar systems for mitigation of volcanic cloud hazards to aircraft Keflavik, Iceland Based on paper by C. Lacasse, S. Karlsdóttir, G Larsen, H Suusalu, W I Rose and G G J Ernst, 2003 Weather radar observations of the Hekla 2000 eruption cloud, Iceland, Bulletin of Volcanology 66:457-473 William I Rose Michigan Technological Univ Fall 2009 Ashfall Graduate Class lecture

2. Meteorological Radar Systems are designed to detect “large” (raindrop-sized) particles such as those found in thunderstorms. They are pulsed, active remote sensing systems which send and receive electromagnetic radiation with wavelengths of 3- 10 cm. The strength of radar return from a cloud is measured in dBz, a unit which is based on relative numbers of mm sized raindrops in a specific volume of cloud. Large particles produce MUCH stronger returns than small ones--the relationship scales to the SIXTH POWER of the radius. The detection is excellent for particles that are cm sized, and very poor for particles smaller than 1 mm….

4. Explosive Eruption +15 sec.+30 sec. +40 sec. +60 sec.+5 min.

5. Eruption Column Rise

6. Ash Fall Rate

7. Volcanic Clouds can only be distinguished by radar if large particles are present. But such particles must fall quickly… So radar mapping becomes problematic after the volcanic cloud is more than 30 min old and the large particles have fallen out. Practical Strategy: Use the radar during eruption and immediately after it. Obtain height information and determine the direction and speed of movement. Then, if you wish to track it after that--you need another tool (eg infrared satellite data).

8. Schneider et al, 1995, USGS Bull 2139: 27- 36 Sept 17-20, 1992

9. 2000 Eruption of Hekla Hekla –Elongate Shield Volcano –Regular series of eruptions (1845, 1947, 1970, 1980, 1991) –Began eruption on Feb 26, 2000 at 1800 UT –Silicic explosive onset to eruptions –Brief explosions followed by fissure fed lava flows Explosive onset Fissure activity and lava flows--main phase Older Hekla silicic fall deposits

10. 26 Feb 2000 1835 UT Ground view of Hekla eruption column, as seen from Vik, Iceland, ~67 km SSE of the volcano (J. Erlendsson)

11. Remote sensing of the brief explosive phase of the eruption shows development of cold cloud with shadows, winds and temperatures reflecting the tropopause. DMSP VIS 2/26/00 1815 UT shadow Rose et al, 2003, AGU Geophys Monograph 139

15. Range-height diagram for Keflavik radar, applicable during the Hekla eruption. Shaded region shows detection limits.

16. The maximum height limit set on the Keflavik radar was determined based on meteorological, not volcanological criteria. Although there may be advantages during routine operations when there is no eruption, this decision unfortunately limited the ability of the radar to measure the maximum height of the eruption cloud. The farther the volcano is from the radar, the more the minimum height is affected---this is due to curvature of the earth. Thus the early onset of explosive eruptions will be missed for more distant volcanoes. The overall maximum range of the radar is listed at 480 km, but practically this is an overestimate, because of curvature.

17. 100 km Hekla Vertical Maximum Intensity VMI “normal” before erupttion

19. Keflavik Radar 26 Feb 2000 1820 UT VMI normal Lacasse et al, 2004, Bull Volcanology Hekla

20. Keflavik Radar 26 Feb 2000 1830 UT VMI normal Lacasse et al, 2004, Bull Volcanology

21. Keflavik Radar 26 Feb 2000 1840 UT VMI normal Lacasse et al, 2004, Bull Volcanology

22. Keflavik Radar 26 Feb 2000 1850 UT VMI normal Lacasse et al, 2004, Bull Volcanology

23. Keflavik Radar 26 Feb 2000 1900 UT VMI normal Lacasse et al, 2004, Bull Volcanology

24. Keflavik Radar 26 Feb 2000 1910 UT VMI normal Lacasse et al, 2004, Bull Volcanology

25. Keflavik Radar 26 Feb 2000 1920 UT VMI normal Lacasse et al, 2004, Bull Volcanology

26. Keflavik Radar 26 Feb 2000 1930 UT VMI normal Lacasse et al, 2004, Bull Volcanology

27. Keflavik Radar 26 Feb 2000 1940 UT VMI normal Lacasse et al, 2004, Bull Volcanology

28. Keflavik Radar 26 Feb 2000 2015 UT VMI normal Lacasse et al, 2004, Bull Volcanology

29. Keflavik Radar 26 Feb 2000 2045 UT VMI normal Lacasse et al, 2004, Bull Volcanology

30. Keflavik Radar 26 Feb 2000 2130 UT VMI normal Lacasse et al, 2004, Bull Volcanology

31. Keflavik Radar 26 Feb 2000 2200 UT VMI normal Lacasse et al, 2004, Bull Volcanology

32. Keflavik Radar 26 Feb 2000 2230 UT VMI normal Lacasse et al, 2004, Bull Volcanology

33. Keflavik Radar 26 Feb 2000 2300 UT VMI normal Lacasse et al, 2004, Bull Volcanology

34. Keflavik Radar 27 Feb 2000 0000 UT VMI normal Lacasse et al, 2004, Bull Volcanology

35. Keflavik Radar 27 Feb 2000 0100 UT VMI normal Lacasse et al, 2004, Bull Volcanology

36. Keflavik Radar 27 Feb 2000 0230 UT VMI normal Lacasse et al, 2004, Bull Volcanology

37. Keflavik Radar 27 Feb 2000 0400 UT VMI normal Lacasse et al, 2004, Bull Volcanology

38. Keflavik Radar 27 Feb 2000 0639 UT VMI normal Lacasse et al, 2004, Bull Volcanology

39. Volcanic cloud rose quickly during eruption and expanded to the NE for several hours. The strength of the radar return is high (>60 dBz)--values that are consistent with very large raindrop-sized particles (lapilli). We expect this radar return to decay quickly (~30 min) from inevitable ash fallout as soon as the eruption wanes. In this case, the eruption wanes, but the radar reflection does not decline as quickly as expected… We infer that residual fine ash, still in the drifting cloud, but not itself detectable by radar, is nucleating ice formation and this process preserves the radar signal longer.

40. Hekla

41. Keflavik Radar 26 Feb 2000 1820 UT EchoTop Lacasse et al, 2004, Bull Volcanology Hekla

42. 26 Feb 2000 1830 UT EchoTop Lacasse et al, 2004, Bull Volcanology Keflavik Radar

43. 26 Feb 2000 1840 UT EchoTop Lacasse et al, 2004, Bull Volcanology

44. Keflavik Radar 26 Feb 2000 1850 UT EchoTop Lacasse et al, 2004, Bull Volcanology

45. Keflavik Radar 26 Feb 2000 1900 UT EchoTop Lacasse et al, 2004, Bull Volcanology

46. Keflavik Radar 26 Feb 2000 1910 UT EchoTop Lacasse et al, 2004, Bull Volcanology

47. Keflavik Radar 26 Feb 2000 1920 UT EchoTop Lacasse et al, 2004, Bull Volcanology

48. Keflavik Radar 26 Feb 2000 1930 UT EchoTop Lacasse et al, 2004, Bull Volcanology

49. Keflavik Radar 26 Feb 2000 1940 UT EchoTop Lacasse et al, 2004, Bull Volcanology

50. Keflavik Radar 26 Feb 2000 2015 UT EchoTop Lacasse et al, 2004, Bull Volcanology

51. Keflavik Radar 26 Feb 2000 2045 UT EchoTop Lacasse et al, 2004, Bull Volcanology

52. Keflavik Radar 26 Feb 2000 2130 UT EchoTop Lacasse et al, 2004, Bull Volcanology

53. Keflavik Radar 26 Feb 2000 2200 UT EchoTop Lacasse et al, 2004, Bull Volcanology

54. Keflavik Radar 26 Feb 2000 2230 UT EchoTop Lacasse et al, 2004, Bull Volcanology

55. Keflavik Radar 26 Feb 2000 2300 UT EchoTop Lacasse et al, 2004, Bull Volcanology

56. Keflavik Radar 27 Feb 2000 0000 UT EchoTop Lacasse et al, 2004, Bull Volcanology

57. Keflavik Radar 27 Feb 2000 0100 UT EchoTop Lacasse et al, 2004, Bull Volcanology

58. Keflavik Radar 27 Feb 2000 0230 UT EchoTop Lacasse et al, 2004, Bull Volcanology

59. Keflavik Radar 27 Feb 2000 0400 UT EchoTop Lacasse et al, 2004, Bull Volcanology

60. Keflavik Radar 27 Feb 2000 0639 UT EchoTop Lacasse et al, 2004, Bull Volcanology

64. Here successive radar images are used to measure the advancing, advecting volcanic cloud, reflecting the dispersion by winds. At left 4 successive images are superimposed with the leading edge of 15 dBz. At right are maps made from such images

65. Here a radar map 2 hrs after the eruption onset is compared with an ashfall map. They are similar, but ashfall occurred slightly westward of the radar position. We infer that the ash was advected westward during its fall through the troposphere by winds.

66. Radar observations, 26 February 2000, eruption of Hekla Column Height > 12 km Most Explosive Eruption duration 1-2 hrs, correllates with seismic record Cloud drifts to NNE, 30-50 m/sec Radar reflections range up to >60 dBz above the volcano, fade after a few hours to near 0 Downwind portion of the volcanic cloud fades slowly, reflecting ice nucleation by finer ash Fallout of ash occurs in area which reflects advection of falling ash by lower level winds

68. Other references about radar detection of volcanic clouds Marzano, F S, G Vulpiani and W I Rose, 2006, Microphysical Characterization of Microwave Radar Reflectivity due to Volcanic Ash Clouds, IEEE Transactions on Geoscience and Remote Sensing 44:313-327. Marzano, F S, S Barbieri, G Vulpiani and W I Rose, 2006, Volcanic ash cloud retrieval by ground-based microwave weather radar, IEEE Trans on Geoscience and Remote Sensing 44: 3235-3246.

69. Weather Radar online http://www.rap.ucar.edu/weather/radar/ http://www.weatheroffice.gc.ca/radar/index_e.html http://www.wunderground.com/radar/map.asp

70. The February-March 2000 Eruption of Hekla, Iceland from a satellite perspective W I Rose, Y Gu, I M Watson, T Yu, GJS Bluth, A J Prata, A J Krueger, N Krotkov, S Carn, M D Fromm, D E Hunton, G G J Ernst, A A Viggiano, T M Miller, J O Ballentin, J M Reeves, J C Wilson, B E Anderson and D E Flittner 2003, AGU Geophysical Monograph 139 (ed by A Robock and C Oppenheimer) 107-132 A detailed study of the Hekla volcanic cloud was made using satellite remote sensing methods and was reported in a paper published last year…

75. Total mass of fine particles in the Hekla volcanic cloud peaks at ~ 10^6 tonnes and decreases after 10 hours.

76. 28 Feb 2000 1115 UT 7.3  m 0.16 Tg8.6  m 0.16-0.24 Tg

77. Eruption Summary Magma erupted: 0.11 km 3 = 3 x 10 5 Tg, mostly long after explosive phase Ice in stratospheric cloud = 1 Tg SO 2 in stratospheric cloud 150-240 kT (MODIS 7.3 and 8.6) Sulfate in stratospheric cloud 3-5 kT Fine ash mass ~100 kT --only detected in first hour