Fig. 3

An example photograph of plumes viewed from Takigoshi station taken on 15 August 2015. The photos were provided from JMA. By tracking of movements of the identical portion of the plume over consecutive images, we estimated wind velocity u and coefficient of the plume shape C₁, in a local coordinate of x, horizontal distance from a reference point, and h, which is vertical distance from a reference point, and then plume heat flux \(\dot{Q}_{\text{h}}\) (see text for the detail of analysis procedure)