Re: double tide cause

[Jim Green <JMGreen@SISNA.COM>]

> I am starting to suspect that the twenty plus harmonics associated
> with current predictors were not intended to model identified
> perturbing forces (after the first four or five ...)
> - I am guessing that the higher harmonics simply
> shape the model waveform to the observed time progress of the
> tide at representative positions.

Brian, NOAA uses sort of a mixture of what you say: first they take the
tidal data/time then do a Fourier-like transform of their own devising and
THEN identify the source of the applied force from the associated
frequency.  As I recall they come up with some 72 frequencies.  In the
process, they form predictive tables. -- I think that these are now on the
web -- It used to be that they sold a DOS program and the appropriated
parameters for a given location and then one printed out  one's own tables.


Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen