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Taryn M. Lopez University of Alaska Fairbanks May 2007

Comparison of OMI SO 2 Satellite Data with Airborne Measurements from the 2006 Fourpeaked Eruption. Taryn M. Lopez University of Alaska Fairbanks May 2007. Projective Objectives. Compare Fourpeaked SO 2 emissions measured from gas flights with OMI derived SO 2 product

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Taryn M. Lopez University of Alaska Fairbanks May 2007

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  1. Comparison of OMI SO2 Satellite Data with Airborne Measurements from the 2006 Fourpeaked Eruption Taryn M. Lopez University of Alaska Fairbanks May 2007

  2. Projective Objectives • Compare Fourpeaked SO2 emissions measured from gas flights with OMI derived SO2 product • Evaluate OMI as a potential tool to be integrated into the existing AVO – Remote Sensing monitoring routine

  3. Background Photo by Lanny Simpson on 9/17/06

  4. Fourpeaked Eruption, 2006 • 9/17/06 at 12:00 PM AKDT • ash cloud detected at 6,000 m above sea level • Prior to this, Fourpeaked was not classified as an active volcano • Gas flights on 9/23/06 and 9/24/06 detected 2,000 + tonnes per day of SO2 • Degassing, small explosions, and variable seismic activity have continued since September www.avo.alaska.edu

  5. Location Map for Fourpeaked Volcano Fourpeaked

  6. OMI Background/Specifications • OMI = Ozone Monitoring Instrument • Flown on the EOS-Aura Spacecraft • Aura was launched on July 15, 2004 • Daily global coverage (14 orbits) • 2600 Km swath width • 13 x 24 Km spatial resolution at nadir • 3 sampling modes: Global, Spatial Zoom in, Spectral Zoom in Schobert et al., 2006

  7. OMI Specifications • Hyperspectral UV/VIS spectrometer • Measures solar backscatter radiation • Uses non-scanning, wide-angle, nadir pointing, push-broom, imaging spectrograph • 1560 wavelength bands from 270-500 nm with a spectral resolution of 0.5 nm • Measures trace gases including: O3, NO2, HCHO, BrO, OClO, and SO2 • Also measures aerosol characteristics, cloud top heights, cloud coverage, and surface UV irradiance. Ahmad et al., 2003

  8. COSPEC • COSPEC – Correlation Spectrometer • Principal tool for remote measurements of SO2 since 1970’s • Measures UV radiation from 300 – 315 nm, specifically 9 peaks and troughs of the SO2 absorption curve • Spinning disk allows transmission of light only for those exact wavelengths • Compares the measured absorption by SO2 against known calibration cells to determine amount of SO2 present in the plume (units of ppmm) Elias et al., 2005

  9. COSPEC at Mount St. Helens Photo by Lyn Topinka, USGS 1983

  10. Methods

  11. Methods • Looked at 8 days throughout the eruption that corresponded with gas flights, only 4 days with OMI SO2 at 5 km: 9/23/06; 9/24/06; 9/30/06; and 10/12/06 • Dates after October 12 did not have OMI SO2 products for 5 km– low UV?

  12. Gas Flight Traverses 9/23/06 Data provided by Mike Doukas USGS-VEP

  13. Converting OMI Data Granules into Images • Free OMI data from: http://disc.sci.gsfc.nasa.gov/data/datapool/OMI/Level2/OMSO2/ • Select date and spatial subset • Download appropriate data granules (up to 14) • OMI data files are in HE5 format • Open data files in HDF Explorer • I was interested in 3 things: SO2 Column Amount at 5 km, Latitude, and Longitude • In HDF Explorer I could view a map of the data and could export data as text files • Produce map in ArcMap and interpolate between the data values

  14. HDF Explorer MapsLeft: SO2 Column Amount (15 Km)Right: Terrain Height(data for 9/23/06)

  15. Results

  16. Results 9/23/06 • Gas flight T1: • Max SO2 = 665 ppmm (~66.5 DU) • Average SO2 = 328 ppmm (32.8 DU) • Plume width ~2 Km • Plume Length estimated to be ~6 Km • Plume Area ~12 Km2 • OMI Pixel ~ 13 x 42 Km (546 Km2) (not at nadir) SO2 value for nearest OMI pixel = 0.24 DU

  17. OMI Swath for 9/23/06 Overlain on Alaska Shapefile

  18. Fourpeaked Measurements 9/23/06(Kriging Interpolation)

  19. Gas Flight Traverse 1 Overlain on OMI Interpolation (9/23/06)

  20. 0 DU 4.77 Km 32.8 DU 23.4 Km Traverse 1: Assume Plume Area of 22.8 Km2 For 32.8 DU = 747.84 DU*Km2Pixel Area (not at nadir) = 13 x 42 Km (546 Km2) (assume 0 DU for remainder of Pixel)747.84 DU*Km2 + 0*534DU*Km2 = 546XX = 1.37 DU = Average Pixel ValueOMI Measured SO2 = 0.24 DU

  21. Gas Flight Traverses 1, 5 & 7 Overlain on OMI Interpolation

  22. 0 DU 4.77 Km 32.8 DU 23.4 Km Traverse 7: Assume Plume Area of 60 Km2 For 18.9 DU = 1134 DU*Km2Pixel Area (not at nadir) = 13 x 42 Km (546 Km2) (assume 0 DU for remainder of Pixel) 1134 DU*Km2 + 0*534DU*Km2 = 546XX = 2.1 DU = Average Pixel ValueOMI Measured SO2 = 0.24 DU

  23. Fourpeaked 9/23/06 Zoomed Out

  24. Puff Model 9/23/06

  25. Puff Model 9/23/06

  26. Puff Model 9/23/06

  27. Fourpeaked 9/24/06 Results(IDW Interpolation)

  28. Puff Model 9/24/06

  29. Puff Model 9/24/06

  30. Puff Model 9/24/06

  31. Fourpeaked Results 9/30/06(IDW Interpolation)

  32. Puff Model 9/30/06

  33. Puff Model 9/30/06

  34. Puff Model 9/30/06

  35. Discussion & Conclusions

  36. Discussion • OMI does appear to have been able to detect SO2 emitted from Fourpeaked volcano • SO2 values are not significantly above noise levels • Puff models in general support plume locations • The values detected using OMI were lower than the airborne measurements (1.37 DU calculated for airborne vs. 0.24 for OMI) • The spatial resolution (13 x 24 Km at nadir or larger for off nadir) is a limiting factor in detecting passive degassing from volcanoes by OMI

  37. Conclusions • OMI data compared fairly well to airborne measurements once a spatial correction was applied (many assumptions in this calculation) • While OMI is able to detect “passive” degassing emissions – these emissions must have very high SO2 concentrations or have a large plume area to distinguish from noise • Because anomalies are not much higher than noise, false alarms could result if used for monitoring purposes

  38. Conclusions Continued • OMI may not be useful for monitoring high latitude volcanoes in winter (this requires further investigation) • Automated processing routine and spatial zoom-in modes would greatly increase the usefulness of this technique • More testing would need to be done to determine if OMI would be a useful monitoring tool (benefits outweigh costs)

  39. Acknowledgements • Anupma Prakash (UAF) • Rudi Gens (UAF) • Mike Doukas (USGS-VEP) • Cindy Werner (USGS-VEP) • Ken McGee (USGS-VEP) • Chris Nye (Alaska DGGS) • Simon Carn (University of Maryland-NASA) • Suraiya Ahmad (NASA) • Lovro Valcic (UAF) • Peter Webley (UAF) • Peter Rinkleff (UAF)

  40. Thanks for Listening! Questions?

  41. NASA Products 9/17/06

  42. My Processing of “Same” File (9/17/06 Orbit 11573): Note Swath Edge

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