Volcanic eruptions: Introduction to remote sensing techniques for fine ash and SO2 detection

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1 Volcanic eruptions: Introduction to remote sensing techniques for fine ash and SO2 detection Bernie Connell Cooperative Institute for Research in the Atmosphere Colorado State University USA

2 Ash clouds are not an everyday issue and they do not provide frequent hazard. But if encountered, volcanic ash can spoil your entire day. (Engen, 1994)

3 Volcanoes of the World Smithsonian Institution, Global Volcanism Program

4 Outline Hazards on the Ground and in the Air Health hazards Aviation hazards Satellite techniques for detection of fine ash and SO 2 Single channel: visible, infrared Combinations using channels across the spectrum: short and long wave infrared, water vapor Contextual observations

5 Objectives Become aware of issues associated with volcanic hazards. Gain exposure to satellite techniques used to detect volcanic ash and SO 2

6 Volcanic Eruptions Two Broad Categories: Effusive eruptions Dominated by passive emission of lava. Explosive eruptions Dominated by the eruption of pyroclastic material. Kilauea Volcano Hawaii Photo by J. D. Griggs 31 January 1984 Mayon Volcano, Phillipines Photo by C.G. Newhall 23 September

7 Volcanic ash, dust, and fragments Volcanic (coarse) ash Volcanic dust (fine ash) up to 2 mm < 62.5 µm Bombs Tephra Photo by C. Heliker 26 January 1988 Photo by J. P. Lockwood 10 July 1982 Photo by D. E. Wieprecht 18 May 1980 Mount St. Helens Single ash particle Ash Block Photo by D. E. Wieprecht 18 May 1980 SEM image provided by A. M. Sarna-Wojcicki

8 Many Hazards on the Ground Mud and debris flows, flash flooding, wildland fires, and hot ashflows. Irritant to eyes, skin and respiratory systems Ash and Gases - SO 2, CO 2, and HF (acid) Collapsed roofs due to heavy ash fall Affects power systems, machinery Impacts to ground transportation (slippery surfaces) Destroys vegetation, affects food sources for people and animals. Affects waterways Photo by E. Endo October 1994 Photo by W. E. Scott 23 June

9 IVHHN The International Volcanic Health Hazard Network

10 Volcanic hazards to airports 1944 through airports in 28 countries affected on 171 occasions from eruptions at 46 volcanoes Since 1980, five airports per year on average have been affected by volcanic activity Guffanti et al Volcanic Hazards to airports. Natural Hazards 51:

11 Hazards in the air Ash and sulfate aerosol can cause significant damage to airframes, and engine components in-flight engine loss windshield abrasion/crazing instrument damage Ash avoidance causes substantial delays in flight operations Unknown health hazards associated with gases 11

12 Important Aviation Considerations Ash column height. Column rise rate. Fine ash concentration. The duration of the ash clouds. From Self and Walker, 1994

13 How is the ash/aerosol plume distinguished on satellite imagery? Use of single and multi-channel imagery: Visible, infrared 10.7 um um temperature difference 8.5 um um temperature difference 3.9 um um radiance/temperature difference

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15 Sensitivity of eruption height to tropospheric instability Relatively weak eruptions in moist tropics can trigger deep convection columns (15-20 km) The same eruptive intensity in dry subpolar environments may produce a lower height (~9 km difference). Tupper et al Rapid growth of ash cloud used for early detection by Mike Pavlonis (NOAA/NESDIS)

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17 GOES 8 1km visible 3 November :15 UTC Reventador Volcano, Ecuador

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19 GOES 8 4km IR 10.7 µm 3 November :15 UTC Reventador Volcano, Ecuador

20 Context not normal dirty - visible deep convection at unexpected time movement of cloud in unexpected direction Visible IR 10.7 µm 3 November :45 UTC Reventador Volcano, Ecuador

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22 GOES 8 4km Reflectivity Prod. using IR 3.9 µm and 10.7 µm 3 November :15 UTC Reventador Volcano, Ecuador

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24 GOES 8 4km Brightness Temperature Difference using IR 10.7 µm and 12.0 µm 3 November :15 UTC Reventador Volcano, Ecuador

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30 Large positive BDT of µm indicates small ice particles Reflectivity product also indicates small ice particles Other measurements co-locate SO 2 (with small ice particles) Thick/opaque cloud shows no ash signal Large negative BDT of µm indicates ash dust. Large negative BTD of µm indicates small ash particles and co-located SO2

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36 Using hyperspectral AIRS data Greater SO 2 absorption at 7.4 um than surrounding WV channels BT (7.778 um 7.435) um > 0

37 SO 2 detection Greater SO 2 absorption at 7.4 um than surrounding WV channels BT um BT um > 0 Lesser SO2 absorption at 8.5 um (than at 7.4 µm) + Ash absorption at 8.5 um BT 8.5 um BT 12.0 um < 0

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45 Blowing Volcanic Dust October 2011 Previous ash and a little new ash from Volcano Cordon Caulle in Chile

46 Blowing Volcanic Dust 16 October 2011 Previous ash from Volcano Cordon Caulle in Chile

47 Points to take away Volcanic eruptions are variable and occur in variable environments. Can consist of ash dust, water, SO2, or a combination of these and other constituents. Main detection of ash dust BTD µm < 0 Detection of SO2 with 8.5µm channel and 7.4 µm.