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

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

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)

Volcanoes of the World Smithsonian Institution, Global Volcanism Program http://www.volcano.si.edu/world/find_regions.cfm

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

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

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 1984 6

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 http://volcanoes.usgs.gov/images/pglossary/

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 1991 8

IVHHN The International Volcanic Health Hazard Network www.ivhhn.org

Volcanic hazards to airports 1944 through 2006 101 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. 2009. Volcanic Hazards to airports. Natural Hazards 51:287-302.

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

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

How is the ash/aerosol plume distinguished on satellite imagery? Use of single and multi-channel imagery: Visible, infrared 10.7 um - 12.0 um temperature difference 8.5 um - 10.7 um temperature difference 3.9 um - 10.7 um radiance/temperature difference

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. 2009 Rapid growth of ash cloud used for early detection by Mike Pavlonis (NOAA/NESDIS)

GOES 8 1km visible 3 November 2002 19:15 UTC Reventador Volcano, Ecuador

GOES 8 4km IR 10.7 µm 3 November 2002 19:15 UTC Reventador Volcano, Ecuador

Context not normal dirty - visible deep convection at unexpected time movement of cloud in unexpected direction Visible IR 10.7 µm 3 November 2002 16:45 UTC Reventador Volcano, Ecuador

GOES 8 4km Reflectivity Prod. using IR 3.9 µm and 10.7 µm 3 November 2002 19:15 UTC Reventador Volcano, Ecuador

GOES 8 4km Brightness Temperature Difference using IR 10.7 µm and 12.0 µm 3 November 2002 19:15 UTC Reventador Volcano, Ecuador

Large positive BDT of 10.7 12.0 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 10.7 12.0 µm indicates ash dust. Large negative BTD of 8.5-12.0 µm indicates small ash particles and co-located SO2

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

SO 2 detection Greater SO 2 absorption at 7.4 um than surrounding WV channels BT 7.778 um BT 7.435 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

Blowing Volcanic Dust 16-18 October 2011 Previous ash and a little new ash from Volcano Cordon Caulle in Chile

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

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 10.7-12.0 µm < 0 Detection of SO2 with 8.5µm channel and 7.4 µm.