Temporal evolution of the 577 individual swirls in 350 swirl locations. The horizontal dashed line represents the time of the slight displacement of the FoV (see Fig. 3). The green lines represent the temporal evolution of the 487 out of 577 swirls that lie within the selected common FoV. The blue lines represent the temporal evolution of swirls that cannot be followed through the entire time sequence due to the displacement of the FoV.