NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: New Moon, Perigee, and Solstice
From: Rodney Myrvaagnes
Date: 2003 Dec 31, 00:02 -0500
From: Rodney Myrvaagnes
Date: 2003 Dec 31, 00:02 -0500
Trevor, I don't know any oceanographers to consult on this question, but lacking anything to break spherical symmetry, I can't see how tides on a spherical earth could be different in one place from another exactly equivalent place. Phase would have to be tied to LHA of the sun and moon, AFIK. Perhaps I misunderstand your meaning. On Tue, 30 Dec 2003 02:07:56 +0000, Trevor J. Kenchington wrote: >Rodney, > >Of course the frequency of tidal waves is not affected by basin >morphology (except where shallow-water effects produce assorted >harmonics in addition to the tide at the frequency of the driving >force). However, it is not only amplitude that is affected by real >basins and would be by the seabed in a theoretical, global ocean of >uniform depth. The phase angles are strongly affected also but, perhaps >more important, so is the nature of the wave. In most areas, tides >predominantly take the form of standing waves and very commonly Kelvin >waves (thus forming amphidromic systems), rather than progressive waves >heading in a westerly direction around the globe. > >That is true in the real Southern Ocean (which is open clear around all >360 degrees of longitude, with a relatively constant depth) as it is in >the open expanses of the real Pacific Ocean. As best as I can comprehend >the conclusions of tidal specialists, it would also be true of the >hypothetical global ocean too. > > >Trevor Kenchington > > > >You wrote: > > >> The depth would certainly have an effect on surface waves as you say, >> but it would affect the amplitude, not the frequency. The solution >> would still be at the frequency of the driving force in the steady >> state. >> >> That is the actual case now, with all the extra complications. It would >> not be less so if the complications were removed. > > >-- >Trevor J. Kenchington PhD Gadus@iStar.ca >Gadus Associates, Office(902) 889-9250 >R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251 >Nova Scotia B0J 2L0, CANADA Home (902) 889-3555 > > Science Serving the Fisheries > http://home.istar.ca/~gadus > > Rodney Myrvaagnes Opinionated old geezer "It is, of course, quite true that no great amount of skill is required to navigate a ship most of the time, and on those less frequent occasions when a higher level of competence is desirable luck may suffice. If that runs out there is always insurance..." __The late Captain Richard Cahill