# Can tides at night by consistently higher than in the daytime? [closed]

Can the tides at night be consistently higher than in the daytime in southwest Australia in the port of Fremantle? Also, what is the explanation for the tides being significant during a part of the year, and then disappear.

• Given your past history with packaged/spam answers (deleted by moderation) to similar questions, are you interested in reasonable input? Because I'm sure some great users would be glad to take their time to give such answers if you are interested in hearing them :) – JeopardyTempest May 23 '18 at 20:43
• @arkaia absolutely, I have no worries over the question, a little edit should be fine. Just noting we (including you) have had interaction with this user before, packaged answers put in many places including here (only visible to users with 2000+ rep). As this looks now, seems only a useful question and answer... only want to alert to past issues, and note concern that this question may look to railroad to a hidden bias. But am very hopeful Юсуп is here with good intentions to learn! – JeopardyTempest May 23 '18 at 21:13
• Are you asking about why tides are higher at night (as per the title), or are you asking why tides come and go over a year in Freemantle (as per the text)? Either way, can you provide any more information on the phenomenon that you're asking about? At the moment I'm voting to close as "unclear what you're asking", but I'd happily vote to re-open if there was a clear description of what you want to know. – Semidiurnal Simon May 24 '18 at 9:00
• Thank you for editing the question for consistency. However, you're still asking "why is x?" for an x that is, at first glance, not the case. Can you provide a link or further information to illustrate what you mean? Then we might be able to answer as to why it happens. – Semidiurnal Simon May 25 '18 at 5:05
• As I don't think the original questioner is likely to edit the question, I am proposing some wording that might be more defendable and also useful for other users. – arkaia May 26 '18 at 0:58

I find the statement in the question difficult to believe.Tides have a pretty cyclical period and I doubt the resulting effect is a day-night difference unless only S1 and S2 tidal constituents are important in that location, which I find very unlikely.

In fact, the portal https://www.tide-forecast.com/locations/Fremantle-Australia/tides/latest shows the high tide being larger during the day for the rest of the month of May 2018. That behavior changes in time as one would expect. The dominant frequencies at this location are diurnal tides (mostly a single high tide and low tide per day). The main diurnal tides have a period around 24 hours and in this case the dominant periods are slightly larger than 24 hours.

You can download the hourly data from: http://uhslc.soest.hawaii.edu/data/netcdf/fast/hourly/h175.nc and the resulting time series goes from 1984 to now. Here is the time series for the year 2017. There is no time at which the tide "dissappears". The resulting harmonic analysis (using t_tide) shows that the tidal constituents with amplitudes over about 5 cm are:

Constituent  Period (h)  Magnitude (m)
O1         25.82      0.1206
K1         23.93      0.1667
M2         12.42      0.0525
S2         12.00      0.0465


The dominant constituents are K1 and O1, with comparable amplitudes. The resulting effect of the two main diurnal frequencies is a period slightly over 24 hours. The effect of the semidiurnal constituents (M2, S2) is smaller and can be seen in the first time series as slight humps in May 24-27.

• T_tide: Pawlowicz, R., B. Beardsley, and S. Lentz, "Classical Tidal "Harmonic Analysis Including Error Estimates in MATLAB using t_tide", Computers and Geosciences, 28, 929-937 (2002).
• Comments: University of Cambridge Forum thenakedscientists.com/forum/index.php?topic=73127.0 – Юсуп May 24 '18 at 8:51
• @Юсуп This site is not a platform to ask questions with the goal of furthering your work (or the work of people you are connected with). If you'd like to seek constructive input on these theories, you could try asking one direct question as to its validity. – JeopardyTempest May 24 '18 at 11:05
• I don't know if much of these practices are a language barrier causing some confusion, or if it's someone pushing more in line with pseudoscience. Unfortunately I never really touched much on oceanography besides certain ocean-atmospheric couplings (namely in ENSO). arkaia (and other oceanograhers) your input would help a lot... does the stuff that keeps getting posted by Юсуп have some connections to the field? Have you heard of the "Eastern European Scientific Journal"? Is this wikipedia term/topic valid, or should it likewise be deleted? – JeopardyTempest May 24 '18 at 11:12
• I'm sorry! The interpreter did not give a high-quality translation. – Юсуп May 24 '18 at 17:50
• The amphidromic points are quite REAL! The issue is that they are zero for one specific constituents out of the many constituents that form the tide. So it might be zero for the M2 tide, but the rest are not going to be zero at exactly that location. I'm not going to go into the discussion of questionable journals and all the pseudoscience stuff. Too much for me! – arkaia May 25 '18 at 1:48