Comparison of OMI SOComparison of OMI SO22 Satellite Satellite

Data with Airborne Data with Airborne Measurements from the 2006 Measurements from the 2006

Fourpeaked EruptionFourpeaked Eruption

Taryn M. LopezTaryn M. Lopez

University of Alaska FairbanksUniversity of Alaska Fairbanks

May 2007May 2007

Projective ObjectivesProjective Objectives

1.1. Compare Fourpeaked SOCompare Fourpeaked SO2 2 emissions emissions

measured from gas flights with OMI measured from gas flights with OMI derived SOderived SO22 product product

2.2. Evaluate OMI as a potential tool to be Evaluate OMI as a potential tool to be integrated into the existing AVO – integrated into the existing AVO – Remote Sensing monitoring routineRemote Sensing monitoring routine

Photo by Lanny Simpson on 9/17/06Photo by Lanny Simpson on 9/17/06

BackgroundBackground

Fourpeaked Eruption, 2006Fourpeaked Eruption, 2006

• 9/17/06 at 12:00 PM AKDT 9/17/06 at 12:00 PM AKDT

• ash cloud detected at 6,000 m above sea ash cloud detected at 6,000 m above sea levellevel

• Prior to this, Fourpeaked was not Prior to this, Fourpeaked was not classified as an active volcanoclassified as an active volcano

• Gas flights on 9/23/06 and 9/24/06 Gas flights on 9/23/06 and 9/24/06 detected 2,000 + tonnes per day of SOdetected 2,000 + tonnes per day of SO22

• Degassing, small explosions, and variable Degassing, small explosions, and variable seismic activity have continued since seismic activity have continued since SeptemberSeptember www.avo.alaska.eduwww.avo.alaska.edu

Fourpeaked

Location Map for Fourpeaked Volcano

OMI Background/SpecificationsOMI Background/Specifications

• OMI = Ozone Monitoring InstrumentOMI = Ozone Monitoring Instrument

• Flown on the EOS-Aura Spacecraft Flown on the EOS-Aura Spacecraft

• Aura was launched on July 15, 2004Aura was launched on July 15, 2004

• Daily global coverage (14 orbits)Daily global coverage (14 orbits)

• 2600 Km swath width2600 Km swath width

• 13 x 24 Km spatial resolution at nadir13 x 24 Km spatial resolution at nadir

• 3 sampling modes: Global, Spatial Zoom 3 sampling modes: Global, Spatial Zoom in, Spectral Zoom inin, Spectral Zoom in

Schobert et al., 2006Schobert et al., 2006

OMI SpecificationsOMI Specifications• Hyperspectral UV/VIS spectrometerHyperspectral UV/VIS spectrometer• Measures solar backscatter radiation Measures solar backscatter radiation • Uses non-scanning, wide-angle, nadir pointing, Uses non-scanning, wide-angle, nadir pointing,

push-broom, imaging spectrographpush-broom, imaging spectrograph• 1560 wavelength bands from 270-500 nm with a 1560 wavelength bands from 270-500 nm with a

spectral resolution of 0.5 nmspectral resolution of 0.5 nm

• Measures trace gases including: OMeasures trace gases including: O33, NO, NO22, ,

HCHO, BrO, OClO, and SOHCHO, BrO, OClO, and SO22

• Also measures aerosol characteristics, cloud top Also measures aerosol characteristics, cloud top heights, cloud coverage, and surface UV heights, cloud coverage, and surface UV irradiance.irradiance.

Ahmad et al., 2003Ahmad et al., 2003

COSPECCOSPEC• COSPEC – Correlation SpectrometerCOSPEC – Correlation Spectrometer• Principal tool for remote measurements of SOPrincipal tool for remote measurements of SO22

since 1970’ssince 1970’s• Measures UV radiation from 300 – 315 nm, Measures UV radiation from 300 – 315 nm,

specifically 9 peaks and troughs of the SOspecifically 9 peaks and troughs of the SO22 absorption curveabsorption curve

• Spinning disk allows transmission of light only Spinning disk allows transmission of light only for those exact wavelengthsfor those exact wavelengths

• Compares the measured absorption by SOCompares the measured absorption by SO22 against known calibration cells to determine against known calibration cells to determine amount of SOamount of SO22 present in the plume present in the plume (units of ppmm)(units of ppmm)

Elias et al., 2005Elias et al., 2005

COSPEC at Mount St. HelensCOSPEC at Mount St. Helens

Photo by Lyn Topinka, USGS 1983Photo by Lyn Topinka, USGS 1983

MethodsMethods

MethodsMethods

• Looked at 8 days throughout the eruption Looked at 8 days throughout the eruption that corresponded with gas flights, only 4 that corresponded with gas flights, only 4 days with OMI SOdays with OMI SO2 2 at 5 km:at 5 km:

9/23/06; 9/24/06; 9/30/06; and 10/12/069/23/06; 9/24/06; 9/30/06; and 10/12/06

• Dates after October 12 did not have OMI Dates after October 12 did not have OMI SOSO22 products for 5 km– low UV? products for 5 km– low UV?

Gas Flight Traverses 9/23/06Gas Flight Traverses 9/23/06

Data provided by Mike Doukas USGS-VEPData provided by Mike Doukas USGS-VEP

Converting OMI Data Granules into ImagesConverting OMI Data Granules into Images

• Free OMI data from: Free OMI data from: http://disc.sci.gsfc.nasa.gov/data/datapool/OMI/Level2/OMSO2/

– Select date and spatial subsetSelect date and spatial subset

– Download appropriate data granules (up to 14)Download appropriate data granules (up to 14)

• OMI data files are in HE5 format OMI data files are in HE5 format

• Open data files in HDF ExplorerOpen data files in HDF Explorer

• I was interested in 3 things: SOI was interested in 3 things: SO22 Column Amount at Column Amount at

5 km, Latitude, and Longitude5 km, Latitude, and Longitude

• In HDF Explorer I could view a map of the data and In HDF Explorer I could view a map of the data and could export data as text filescould export data as text files

• Produce map in ArcMap and interpolate between Produce map in ArcMap and interpolate between the data valuesthe data values

HDF Explorer MapsHDF Explorer MapsLeft: SOLeft: SO22 Column Column

Amount (15 Km)Amount (15 Km)Right: Terrain HeightRight: Terrain Height

(data for 9/23/06)(data for 9/23/06)

ResultsResults

Results 9/23/06Results 9/23/06• Gas flight T1:Gas flight T1:

– Max SOMax SO22 = 665 ppmm (~66.5 DU) = 665 ppmm (~66.5 DU)– Average SOAverage SO22 = 328 ppmm (32.8 DU) = 328 ppmm (32.8 DU)– Plume width ~2 KmPlume width ~2 Km– Plume Length estimated to be ~6 KmPlume Length estimated to be ~6 Km– Plume Area ~12 KmPlume Area ~12 Km2 2

• OMI Pixel ~ 13 x 42 Km (546 KmOMI Pixel ~ 13 x 42 Km (546 Km22))(not at nadir)(not at nadir)

SOSO22 value for nearest OMI pixel = 0.24 DU value for nearest OMI pixel = 0.24 DU

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

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

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

Traverse 1: Assume Plume Area of 22.8 KmTraverse 1: Assume Plume Area of 22.8 Km2 2

For 32.8 DU = 747.84 DU*KmFor 32.8 DU = 747.84 DU*Km22

Pixel Area (not at nadir) = 13 x 42 Km (546 KmPixel Area (not at nadir) = 13 x 42 Km (546 Km22) ) (assume 0 DU for remainder of Pixel)(assume 0 DU for remainder of Pixel)

747.84 DU*Km747.84 DU*Km22 + 0*534DU*Km + 0*534DU*Km2 2 = 546X= 546XX = 1.37 DU = Average Pixel ValueX = 1.37 DU = Average Pixel Value

OMI Measured SOOMI Measured SO22 = 0.24 DU = 0.24 DU

32.8 DU

0 DU

23.4 Km23.4 Km

4.77 4.77 KmKm

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

Traverse 7: Assume Plume Area of 60 KmTraverse 7: Assume Plume Area of 60 Km2 2

For 18.9 DU = 1134 DU*KmFor 18.9 DU = 1134 DU*Km22

Pixel Area (not at nadir) = 13 x 42 Km (546 KmPixel Area (not at nadir) = 13 x 42 Km (546 Km22) ) (assume 0 DU for remainder of Pixel)(assume 0 DU for remainder of Pixel)

1134 DU*Km 1134 DU*Km22 + 0*534DU*Km + 0*534DU*Km2 2 = 546X= 546XX = 2.1 DU = Average Pixel ValueX = 2.1 DU = Average Pixel Value

OMI Measured SOOMI Measured SO22 = 0.24 DU = 0.24 DU

32.8 DU

0 DU

23.4 Km23.4 Km

4.77 4.77 KmKm

Fourpeaked 9/23/06 Zoomed OutFourpeaked 9/23/06 Zoomed Out

Puff Model Puff Model 9/23/069/23/06

Puff Model Puff Model 9/23/069/23/06

Puff Model Puff Model 9/23/069/23/06

Fourpeaked 9/24/06 ResultsFourpeaked 9/24/06 Results (IDW Interpolation)(IDW Interpolation)

Puff Model 9/24/06Puff Model 9/24/06

Puff Model 9/24/06Puff Model 9/24/06

Puff Model 9/24/06Puff Model 9/24/06

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

Puff Model 9/30/06Puff Model 9/30/06

Puff Model 9/30/06Puff Model 9/30/06

Puff Model 9/30/06Puff Model 9/30/06

Discussion Discussion & Conclusions& Conclusions

DiscussionDiscussion• OMI does appear to have been able to detect OMI does appear to have been able to detect

SOSO22 emitted from Fourpeaked volcano emitted from Fourpeaked volcano

– SOSO22 values are not significantly above noise levels values are not significantly above noise levels

– Puff models in general support plume locationsPuff models in general support plume locations

• The values detected using OMI were lower than The values detected using OMI were lower than the airborne measurements (1.37 DU calculated the airborne measurements (1.37 DU calculated for airborne vs. 0.24 for OMI)for airborne vs. 0.24 for OMI)

• The spatial resolution (13 x 24 Km at nadir or The spatial resolution (13 x 24 Km at nadir or larger for off nadir) is a limiting factor in detecting larger for off nadir) is a limiting factor in detecting passive degassing from volcanoes by OMIpassive degassing from volcanoes by OMI

ConclusionsConclusions• OMI data compared fairly well to airborne OMI data compared fairly well to airborne

measurements once a spatial correction was measurements once a spatial correction was applied (many assumptions in this calculation)applied (many assumptions in this calculation)

• While OMI is able to detect “passive” degassing While OMI is able to detect “passive” degassing emissions – these emissions must have very emissions – these emissions must have very high SOhigh SO22 concentrations or have a large plume concentrations or have a large plume

area to distinguish from noisearea to distinguish from noise

• Because anomalies are not much higher than Because anomalies are not much higher than noise, false alarms could result if used for noise, false alarms could result if used for monitoring purposesmonitoring purposes

Conclusions Continued

• OMI may not be useful for monitoring high OMI may not be useful for monitoring high latitude volcanoes in winter (this requires further latitude volcanoes in winter (this requires further investigation)investigation)

• Automated processing routine and spatial zoom-Automated processing routine and spatial zoom-in modes would greatly increase the usefulness in modes would greatly increase the usefulness of this techniqueof this technique

• More testing would need to be done to More testing would need to be done to determine if OMI would be a useful monitoring determine if OMI would be a useful monitoring tool (benefits outweigh costs) tool (benefits outweigh costs)

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

Thanks for Listening!Thanks for Listening!

Questions?Questions?

NASA Products 9/17/06NASA Products 9/17/06

My Processing of “Same” File My Processing of “Same” File (9/17/06 Orbit 11573):(9/17/06 Orbit 11573):

Note Swath Edge