Langila, New Britain, Papua New Guinea, 1997

Image source: Animated GMS, processed.

Comments: This sequence shows the difficulty of spotting volcanic ash at certain times of the year; in this case, during the monsoon season when clouds are widespread and the air is heavily loaded with moisture. Red pixels on these images are 'potential ash' results from the subtraction of GMS channels, but in this sequence these are largely false alarms. A few images are missing from the image archive during the day, but careful inspection of the area around Langila, at the upper right, shows eruptions through the day, confirmed by aircraft reports. An aircraft encountered ash to the southwest of the PNG mainland, as seen on the last image frame of the above loop. Tracking ash from the point of eruption to the point of the aircraft encounter is very difficult, even in hindsight.

Image Source: GMS-5 visible, February 11/12, 1997

Comments: The areas outlined in blue on these images are those thought to be ash clouds after careful inspection of the satellite sequence and comparison with aircraft reports..