SO231 General Oceanography 1

Fall 2000  TIDES LAB

 

We will use the TIDES computer program for this lab.  After completing this lab, you should be able to interpret graphs of tidal records and understand the following:

·                     Relationship of the moon phase and declination to tropical, equatorial, spring and neap tides.

·                     Tidal range and diurnal inequality.

·                     Diurnal, mixed, and semi-diurnal tides.

·                     The time between successive tides.

·                     Storm surges.

·                     Partial tides.

 

1.     Open the program and select Moon animation, Both.  You can control the animation (Pause, Stop, and vary the Time Step) using the Moon animation menu choice.

a.      Look at the top view.  What is the effect of the moon phase on the observed tide?

b.     Next look at the side view.  What is the effect of the moon’s declination on the tide?

c.      Are these two processes in phase with each other?  (You could use the Jump option to move to a particular day to see if every month looks the same.)

 

 

 

 

 

 

 

 

 

2..  The F ratio (K1+O1) / (M2+S2) determines the type of tide at a station.  If F < 0.25, the tide is semi-diurnal; if 0.25 < F < 3.0, the tide is mixed; and if F > 3.0, then the tide is diurnal.

 

Station                  M2    S2     K1     O1     F      Type

San Francisco           54     12     37     23

Do-Son, Viet Nam         4      3     72     70

Immingham, England     223     73     15     16

Manila,Phillipines      20      7     30     28

 

Calculate the F ratio for each of these stations, and determine how the tidal records for each type of tide vary.  You  can get the graphs using the Tidal records, Type of tides menu option (Stop the animation if necessary to enable this option.) 


For each of the four tidal curves you used, determine the following (double click on the graph to get a reading at any desired point):

Tidal Range

Diurnal Inequality.  Is a large diurnal inequality related to a diurnal or a semidiurnal tide?

Time of neap and spring times, and duration between them.

Time between high and low tides (blow up the time axis so that you can get meaningful numbers)l

 

 

 

 

 

 

3.     Select Options, Show partials, and display the diurnal and semidiurnal stations you just identified.  You may want to rescale the time axis.  How do the partial tides create the total record, and how do the partial tides vary in these end member stations?

 

 

 

 

 

 

 

 

4.     Compare the tidal records for Annapolis and Hampton Roads (Norfolk) for the first few months of 1990.  You can plot the observed, the predicted, and the difference between these two, all from the Tidal records, NOAA observations menu choice.  Which station has the larger tidal range?  What is the relationship among the predicted and the observed tide? 

 

 

 

 

 

 

 

 

5.  Look at the observed tidal record for Annapolis during Hurricane Fran and the April Fool’s Day storm, from the Tidal Records, NOAA observations, View WWW preliminary records menu choice.  Project what the predicted tide should have been during this time, and what the storms did to it.  What causes the storm to do this?

 

 

 

6.  If you have time and the WWW is not too much of a world wide wait, get the tide data from the station nearest your home (or an exotic port if you are completely landlocked at home).  Use the Get WWW preliminary records menu choice, select a reasonably short time frame (no more than  month), and then save the table as an HTML file that you can view with the View WWW preliminary records menu choice.