Use of GOES thermal infrared imagery for eruption scale measurements, Soufriere Hills, Montserrat

GOES two-band IR data are used to estimate the magnitude of small eruption clouds (< 10(7) metric tonnes of total ash; <similar to 10(5) tonnes of fine [1-25 mu m in diameter] ash, and 5-15 km asl). The method is demonstrated on clouds from Soufriere Hills Volcano, Montserrat in 1997-99. The clouds in early 1999 were much smaller, were generally emplaced lower in the atmosphere and contained an order of magnitude less fine ash than 1997 clouds generated during the most intense phase of the eruption to date. Although GOES has an excellent capability for large eruption clouds, its use for smaller eruptions like Montserrat highlights several shortcomings, including atmospheric water vapor and instrument noise. In spite of these shortcomings, GOES time series data can measure differences in intensity of eruptions, and be of particular value in monitoring where ground-based observations are sparse.