Lowest and highest astronomical tides

[MCC]

Some help for a lurker, please.
According to my Tide Table booklet for Falmouth for this year the
Highest Astronomical Tide will occur at 0624 GMT on 2nd March 2010 and
the Lowest Astronomical Tide will occur att 0039 GMT on 22nd March 2015.
Apart from the fact that these tides will occur two days after a Full
and New Moon respectively, as is normal for all Spring Tides, what other
phenomena will occur to cause these tides to be so high and so low?
--
MCC

[Jonathan Silverlight]

In message <472w8vspx3wx.120r9mi279jen.dlg@40tude.net>, MCC
<mcc5959@hotmail.com> writes

I'm embarrassed to say I'd never heard of Astronomical Tides (and having
looked it up I'm amused to see that <http://www.pcwp.com/tide.html>
refers to "astrological tides" ! )
But I would guess that the common factor is that both tides occur when
the Moon is near perigee (28 February 2010 and 20 March 2015) As the LAT
occurs close to midnight, the fact that the Earth, Moon and Sun are all
lined up might also be a factor.
--
Remove spam and invalid from address to reply.

[MCC]

On Tue, 7 Jun 2005 23:13:18 +0100, Jonathan Silverlight wrote:


Thank you - I just hope I'm still around to experience both occasions!
Maybe I should consult an astrological hydrographer.
--
MCC

[Dr John Stockton]

JRS: In article <ns75oZv+vhpCFwNu@merseia.fsnet.co.uk>, dated Tue, 7
Jun 2005 23:13:18, seen in news:uk.sci.astronomy, Jonathan Silverlight
<jsilverlight@spam.merseia.fsnet.co.uk.invalid> posted :



See <URL:http://www.merlyn.demon.co.uk/gravity5.htm#Tides>.

Sea-tides are mainly caused by the lunar gravity gradient (with a
component from the solar).

"Spring" tides occur when Earth, Sun, and Moon are in line, and the
gradients reinforce; "Neap" tides occur when Sun, Earth, and Moon form a
right angle. Eclipses only occur at Spring Tides.

The tidal effect of a body is proportional to its density & the cube of
its apparent angular diameter, only.

So : further response to Martin F : even the uniform tide on a
body in LLO will be no more than a factor of about ten greater
than the maximum tide exerted on it by those assembling it.


The alignment is more important than the perigee; the Sun's tide is
about 40% of the Moon's, and the Moon's tide varies rather less :

Eccentricity 0.05 (Whipple)
Apoapsis/Periapsis = (1 + e) / (1 - e), say 10%
Lunar tidal field variation thus 30%; +-15%.

--
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