Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: New Moon, Perigee, and Solstice
    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{at}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
    
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site