Volcanic clouds, which are a major aviation hazard, are complex and the background environment in which they reside is often complicated as well. Much of the complexity is due to the multi-composition nature of volcanic clouds, which frequently consist of some combination of volcanic ash, volcanic gases, and hydrometeors. Thus, volcanic cloud remote sensing is very challenging. “Next generation” geostationary meteorological satellites, such as GOES-17, have many more spectral channels, improved spatial resolution, and provide far more frequent images compared to heritage geostationary satellites. The more advanced spectral, spatial, and temporal capabilities of next generation geostationary satellites allow for much improved qualitative and quantitative volcanic cloud remote sensing. The additional spectral channels help to distinguish between volcanic ash and other features and improve the accuracy of ash cloud property retrievals. Spectral channels that are sensitive to volcanic sulfur dioxide (SO2) are also available. The improvement in spatial resolution and the dramatic increase in image frequency results in earlier detection of volcanic emissions and for more robust long term tracking of volcanic clouds. While no single satellite sensor is ideal for detecting and characterizing all volcanic clouds at all times, it will be shown that improved spectral, spatial, and temporal attributes of next generation satellites have a significant positive impact on volcanic cloud identification, tracking, and characterization. The full potential of the next generation geostationary satellites, however, will only be realized if automation is used to supplement manual interrogation of imagery, as daily data volumes are about 100 times greater than the previous generation of satellites.
In an effort to fully utilize next generation geostationary measurements for real-time volcanic cloud applications, National Oceanic and Atmospheric Administration (NOAA), in collaboration with the University of Wisconsin, has developed the Volcanic Cloud Analysis Toolkit (VOLCAT). VOLCAT utilizes many different satellite sensors generate alerts when volcanic unrest or an eruption is detected. VOLCAT also automatically tracks and characterizes volcanic clouds. Through advanced use of spectral, spatial, and temporal information, the VOLCAT algorithms are capable of automatically detecting a broad range of volcanic clouds, including opaque multi-component (ash, ice, and SO2) clouds. Several examples are used to illustrate the value of VOLCAT and next generation satellites, with an emphasis on volcanic activity in the North Pacific.