Ultraviolet Remote Sensing of Volcanic Emissions

Satellite-based ultraviolet remote sensing of volcanic eruptions has produced quantitative measurements of the mass of sulfur dioxide and ash in volcanic clouds by accounting for ozone absorption and Rayleigh scattering in the atmosphere. These retrieval techniques were developed with data from the total ozone mapping spectrometer (TOMS) instruments on American, Russian, and Japanese satellites. The sulfur dioxide retrievals have been validated against ground-based Brewer and COSPEC measurements. The ash mass retrievals are in agreement with AVHRR two-band infrared ash retrievals. Daily satellite monitoring has detected, tracked, and quantified SO 2 emissions from a wide range of eruptive activity, from highly explosive to effusive types, and has produced an unprecedented 20-year record of global volcanism. Primary findings from the TOMS data are (1) observations of excess sulfur over that liberated during liquid-phase degassing have indicated the existence of a volatile phase in preerupted magma; (2) indirect evidence for co-erupted H 2 S gas from apparent increase in SO 2 mass in drifting clouds; (3) insights into the removal rates of SO 2 from the atmosphere, interactions with co-emitted ash particles, and responses to meteorological conditions; and (4) potential operational application of sulfur dioxide and ash detection for aviation hazard mitigation.