Understanding timescales within the day period I stumbled across a timescale which I am unsure of. What does it mean by intra-daily scale variability? I would also like to know if intra-tidal scale variability is of any use for capturing daily physical processes in estuaries (e.g. stratification). Feedback will help me understand when it is appropriate to use these timescales for making scientific predictions.
Intra-daily scale variability is pointing to the circadian rhythms. the circadian rhythms are physical, mental, and behavioral changes that follow a "daily" cycle. They respond primarily to light and darkness in an organism's environment. It is not an accurate time scale, as the light and darkness are not a cycle itself, but it is commonly use on medicine. Google it. I will recommend this.

The Intra-tidal it is used for a few processes linked with the tides, but it is not "just" on daily basis as the tides have not a daily interval. Look there and there

Both timescales are usefull for whatever process linked to human (or animal) bodies and tides. But as scale times, they are not very useful.

Regarding predictions... which kind of predictions are you talking about?