possible.

For each segment, Dopplergrams were filtered in the Fourier domain using an $f$-mode ridge filter [@Langfellner2015] which includes power from wave numbers $300 < kR_\sun < 2600$ with a peak at $kR_\sun \approx 1100$. [Here, $R_\sun$ is the solar radius and $k$ is the horizontal wave number. Next,]{} $f$-mode point-to-annulus [@Duvall1996] travel-time maps [@GB2004] were obtained from the filtered Dopplergrams in the inward minus outward sense. This resulted in maps with $512\times512$ pixels, with each pixel being $(0.348\,\rm{Mm})^2$ in size. These travel-time maps are known to be a proxy of near-surface horizontal divergence of the fluid motion [e.g., @Langfellner2015]. To remove the smallest-scale noise from the data, we low-pass filter this dataset in the Fourier domain and keep Fourier components with $k R_\sun < 1200$.

In addition, we obtained a smoothed version of the (not low-pass filtered) TD maps in order to better compare to earlier results. We used a two-dimensional Gaussian window with full width at half maximum of 5.22 Mm (15 pixels), which is similar to the smoothing done by [@Duvall2000].

[[For all data sets discussed here, the horizontal mean of each map has been removed.]{}]{} Figure \[figDataExamples\] shows example LCT and TD maps. The most prominent 