Parallax-based Height Estimation of the Tonga Volcanic Plume
In this page, the height of the volcanic plume from Hunga Tonga-Hunga Ha‘apai on 2022-01-15 can be estimated from its parallax between the Himawari-8 and GOES-17 satellites.
Although the two satellites observe the plume nearly simultaneously, small lags likely less than a minute are present. Thus, if you measure fast-moving features, its movement can contaminate the parallax and reduce the accuracy of the altitude estimation.
For example, if a cloud is moving eastwards or westwards at 70 m/s and the two satellites observe it with a 60-second lag, its moves 4.2 km during the lag and contaminates the parallax, resulting in an altitude error a little below 2 km.
Northward or southward movement of a cloud does not affect its altitude estimation because the latitude differences are ignored in the estimation.
In the calculation of the parallax, the Earth is assumed to be an ellipsoid.
Infrared images denote brightness temperatures (degC) in Band 13. The color scale is shown below.