Unexpected encounters with volcanic ash by high altitude jet aircraft can cause serious damage to their frames and engines, putting at risk the lives of the passengers and crew. The GOES Visible imagery provides high-resolution, remote detection capability for this hazard during daylight hours. For nighttime detection, multi-channel imaging techniques using the "split window" brightness temperature difference (10.7 µm - 12.0 µm) and the 3.9 µm - 10.7 µm radiance difference have also been used both operationally and by researchers.
The imagery that follows demonstrates the ability of certain GOES Imager channels, alone and in combination, to locate and monitor plumes of volcanic ash during both daylight and night-time hours.
- Figure 1 is a 10.7 µm image showing the ash plume (outlined in yellow) from an October 21, 1997 eruption of the Soufriere Hills Volcano on Montserrat. The volcano had erupted 6.5 hours earlier (during daylight hours), and the plume is still quite distinct.
- Figure 2 shows the 10.7 µm - 12.0 µm brightness temperature difference, in which the main portion of the volcanic ash plume is distinguished by large negative differences.
- Figure 3 is a 3.9 µm image. Notice that the plume is hard to detect.
- Figure 4 is the reflectivity product, the 3.9 µm - 10.7 µm difference, in which the plume is readily distinguished. See previous discussion on the reflectivity product.
- Figure 5 is an experimental product. In order to remove as much background information as possible and show only the ash plume, a 3-channel product using the 3.9 µm, 10.7 µm and 12.0 µm imagery has been created.
