Photospheric and chromospheric raster images of a sunspot, NOAA AR 13798, obtained at Hα + 4 Å and at the Hα line center, respectively, observed on 2024 August 25 at 19:44:57 UT. Black and white contours represent the boundaries of the umbra and penumbra, respectively. The yellow line denotes the slit position used for the time-distance map analysis shown in Fig. 5. Colored “+” symbols mark the five positions used to investigate the temporal variation in the LoS Doppler velocity and their corresponding EMD modes: (a) umbra (orange), (b) penumbra (green), (c) penumbral boundary (red), (d) outer superpenumbra (purple), and (e) inner superpenumbra (blue).