Airborne Volcanic Gas Measurements at Iliamna Volcano, Alaska 2004-2017

This release presents data collected during airborne volcanic gas monitoring flights at Iliamna Volcano, Alaska, that were completed between 2004-2017. Instrumented fixed-wing aircraft were used to collect in situ trace gas measurements of volcanic carbon dioxide (CO2), sulfur dioxide (SO2), and hydrogen sulfide (H2S). The sensor payload also included an upward-looking correlation spectrometer (COSPEC) and/or differential optical absorption spectroscopy (DOAS) system. The remote sensing instruments were used to derive volcanic SO2 emission rates by measuring incident scattered solar ultraviolet radiation while traversing beneath the plume. Gas compositions and COSPEC output (volts) were recorded at 1 Hz and DOAS radiance spectra were collected at approximately 1 Hz depending on the ambient light conditions. All data were stamped with the GPS time and location. Trace gas and COSPEC measurements collected on 16 flights from 2004-2017 are included in a compressed file (GasData_2004_2017_v2.zip) that contains spreadsheets saved in the *.csv format and named using the local date on which the flight occurred in YYYYMMDD format (YYYY = year, MM = month, DD = day). The known values of COSPEC calibration cells used to scale raw measurements and information about gas standards used during in-flight CO2, SO2, and H2S sensor verifications are given in an auxiliary file (GasStandards.csv). DOAS data were collected during 3 flights from 2015-2017; each DOAS spectrum was saved in a separate ASCII file which includes 2048 radiances measured in the 285 - 430 nm spectral region and metadata associated with each acquisition. Additional information concerning the instruments and methods used to collect data from 2004-2007 is available in Doukas and McGee (2007), and in Kelly et al. (2013) and Werner et al. (2013) for data collected after 2007. See the associated publication for analysis and discussion of these data: Werner, C., Power, J., Kelly, P., Prejean, S., & Kern, C., 2021, Characterizing unrest: A retrospective look at 20?years of gas emissions and seismicity at Iliamna Volcano, Alaska. Journal of Volcanology and Geothermal Research, 107448. https://doi.org/https://doi.org/10.1016/j.jvolgeores.2021.107448 References Doukas, M. P., & McGee, K. A., 2007, A compilation of gas emission-rate data from volcanoes of Cook Inlet (Spurr, Crater Peak, Redoubt, Iliamna, and Augustine) and Alaska Peninsula (Douglas, Fourpeaked, Griggs, Mageik, Martin, Peulik, Ukinrek Maars, and Veniaminof), Alaska, from 1995-2006. https://pubs.usgs.gov/of/2007/1400/of2007-1400.pdf Kelly, P. J., Kern, C., Roberts, T. J., Lopez, T., Werner, C., & Aiuppa, A., 2013, Rapid chemical evolution of tropospheric volcanic emissions from Redoubt Volcano, Alaska, based on observations of ozone and halogen-containing gases. Journal of Volcanology and Geothermal Research, 259, 317?333. https://doi.org/10.1016/J.JVOLGEORES.2012.04.023 Werner, C., Kelly, P. J., Doukas, M., Lopez, T., Pfeffer, M., McGimsey, R., & Neal, C., 2013, Degassing of CO2, SO2, and H2S associated with the 2009 eruption of Redoubt Volcano, Alaska. Journal of Volcanology and Geothermal Research, 259. https://doi.org/10.1016/j.jvolgeores.2012.04.012