File:Tonga Volcano Plume Reached the Mesosphere (GOES-17) 15 January 2022.jpg

English: This sequence of still images from GOES-17 shows the plume at various stages on January 15. Note how the tallest parts of the plume in the stratosphere and mesosphere cast shadows down on the lower parts.

Khlopenkov and Bedka used a technique that they originally designed to study severe thunderstorms that penetrate the stratosphere. Their algorithm matches simultaneous observations of the same cloud scene from two satellites, and then uses stereoscopy to construct a three-dimensional profile of elevated clouds. (This is similar to the way the human brain perceives things in three dimensions using two images from our eyes.) Khlopenkov then verified the stereoscopic measurements using the length of the shadows that the tallest plumes cast on the broad ash clouds below. They also compared their measurements with a NASA GEOS-5 model analysis to determine the local height of the stratosphere and troposphere that day.

The uppermost part of the plume sublimated almost immediately due to extremely dry conditions in the mesosphere. However, an umbrella of ash and gas spread out in the stratosphere at an altitude of about 30 kilometers (20 miles), eventually covering an area of 157,000 square kilometers (60,000 square miles), larger than the state of Georgia.