Characterizing Explosive Volcanic Eruptions: A Passive Microwave Satellite Approach

We explore the potential of Passive Microwave (PMW) sensors for analyzing volcanic ash plumes from explosive eruptions. Utilizing data from the Global Precipitation Measurement (GPM) Microwave Imager (GMI) and the Special Sensor Microwave Imager/Sounder (SSMIS), we conducted an examination of three volcanic eruptions with a Volcanic Explosivity Index (VEI) greater than four. These eruptions included the 2021-2022 Hunga Volcano, 2021 Fukutoku-Oko-no-Ba, and the 2019 Raikoke eruptions. Our methodology involved calculating the difference between observed and simulated clear-sky brightness temperatures (∆TB) to isolate the volcanic signal from the background. The simulated background brightness temperatures were derived from radiative transfer simulations, which model the transfer of electromagnetic radiation through the atmosphere, based on ERA-5 reanalysis data. Our findings indicate that PMW sensors can differentiate signals of volcanic eruptions from other meteorological processes using ∆TB. For low frequency channels, we typically see a ∆TB of magnitude less than 10K, while high frequency channels have a ∆TB magnitude of -75K. Notably, volcanic pixels were statistically distinguishable from other meteorological clouds in the atmosphere based on 37H and 150H channels. As PMW observations are insensitive to small ice particles, the technique proposed here provides information on plumes also under conditions where ice clouds limit the usability of traditional infrared and visible sensors.