The use of GOES Sounder imagery for the detection of hazardous volcanic ash plumes

The ability of the GOES atmospheric sounder to track volcanic ash clouds was compared to the GOES imager for eleven eruptions of the Soufriere Hills volcano on Montserrat in the eastern Caribbean during the summer and autumn of 1997. The "split window " two-band tech-nique, based on the brightness temperature difference of the longwave (12.0 11m) and window infrared (10.7 11m) bands was used in the evaluation, validated with high resolution 1 km visible data (0.6 11m). Since most of the volcanic events used in this study occurred in daytime, the visible channel was used to verify the presence of volcanic ash. Based on an evaluation of the cases, the sounder was deemed to be suitable for_detecting significant ash plumes, but with some degradation due to lower resolution. The maximum hourly frequency of the GOES sounder is con-sidered sufficient, but not as desirable as the 15-30 min-utes attainable from the imager. Operational considera-tions regarding the scheduling and implementation of the sounder scan strategy are addressed. Other channels available on the GOES sounders, especially the 3.7 11m band, may also be useful, especially when combined with the split window imagery. 1