Using data from NASA’s Earth Observing System Aura satellite, launched in 2004, a team led by Michigan Technological University created a global map of volcanic emissions. Scientist Nick Krotkov will use the information to refine climate models and better understand the human and environmental health risks of erupted gases like sulfur dioxide.

NASA Tech Briefs: How did these maps of volcanic emissions get made?

Nick Krotkov: First, we use an Ozone Monitoring Instrument (OMI) on the NASA Aura satellite, which is a hyperspectral ultraviolet (UV) and visible spectrometer. The OMI spectrometer measures the spectra of solar radiation backscattering from the Earth’s atmosphere and the surface. On the way through the atmosphere, the light gets absorbed by ozone and other minor gases, which have characteristic absorption features we analyze with retrieval algorithms. Specifically, we look for the characteristic UV spectral absorption lines of sulfur dioxide (SO2) gas, which volcanoes emit.

NTB: What is the Aura satellite?

Krotkov: The Aura satellite is in a lower-Earth orbit, and measures every place on Earth once a day, in early afternoon, and moves with the Sun. We can see SO2 degassing from volcanoes if clouds do not obscure it. SO2 absorption lines have different spectral shapes compared to those for ozone, so we can separate these gases using hyperspectral UV instruments such as the OMI and the operational Ozone Profiling and Mapping Suite (OMPS) onboard the NASA-NOAA Suiomi National Polar Partnership (S-NPP) weather satellite.

NTB: Why are these maps important?

Krotkov: It’s very important to monitor the natural and anthropogenic SO2 sources globally. The SO2 gas that is emitted from volcanoes interacts with water vapor to convert to tiny sulfate particles, which scatter back solar radiation and can cool the climate. The SO2 gas is a pollutant, which is harmful to breathe and can cause irritation of the respiratory system. SO2 causes acidification of the environment, like you can see in the dead forests near the volcanoes. With the satellite, you have a consistent worldwide view of the sources of volcanic gases and anthropogenic pollution. We can now do a “global catalog” of the largest persistent SO2 emitters. Man-made emissions of SO2 can be reduced with technologies and regulations, but volcanoes always will be present, so we need to know accurately what the background is of the volcanic emissions to be able to separate it from the manmade SO2 pollution.

NTB: What did you learn from the OMI measurements?

Krotkov: Overall, OMI measured volcanic degassing emissions. OMI measurements have shown that manmade SO2 emissions were reduced greatly in North America, Europe, and East Asia, mainly because of flue-gas desulfurization devices installed on coal-fired power stations and smelters. At the same time, SO2 emissions have increased in some regions such as northeast India.

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