Fig. 1 compares snapshots and 1-day averages of the vertical component of velocity w at 50 m and at 400 m. As predicted, most of the signal at depth in snapshots is associated with high-frequency internal waves that disappear in the 1-day averages. The signal within the surface mixed layer is reduced but still mostly present because it is believed that it is associated with ageostrophic circulations that are relatively constant over a day.
Figure 1: Comparison of absolute w (vertical component of velocity) between snapshots (left) and 1-day averages (right) at 50 m (upper) and 400 m (lower).
A quick look at an animation does not seem to reveal any obvious pattern of propagation.
The every-3-hour snapshots are read with read_bin.m in RESEARCH/PROJECTS/MARINE_BIOLOGY/SUBMESOSCALE_PROCESSES/HYCOM/routines/ on ipu1.