Distribution plots of times of day of high and low tides. A work in progress.

Roy Tsuda, professor of Marine Botany at the University of Guam, is an enthusiast of tides.  His lecture on the ideas of one of his professors, Max Doty about intertidal zonation made an impression on me.  I'm not sure now, some 35 years later, whether he had something to do with instilling me a strong interest in the times of high and low tides.   I think he did.

In Chuuk Lagoon, I learned that at the time when "a pwopwooisor" (the tide was pregnant or swollen [pwopwo} in the morning [isor], certain bivalves are ripe to eat---with a growth of orange matter, obviously eggs.  I also heard a casual remark that "the tide has changed" in reference to the times of high and low tides.

How to graph this relationship, to analyze and grow our understanding?  Ideas pop out of the graphs, ideas the inkling that prodded me to start in the first place.  These are distribution plots, not a track through time, like a tide calendar.  I want to see what times of day are the tides highest or lowest, and during which months?  When it takes several years to produce something, is it  a work in progress? 

Time of day is the independent variable, the X axis.  Predicted heights are the dependent variable. Different colors encode the months. 

Studying some of the graphs it is apparent that  a "month" is not a natural division of time; in certain cases there are what look like different modes within a "month."  A lunar calendar might work better.  Or maybe not.  Tides are complicated.  Traditional fishermen, without the benefit of calendars, ephemerides, or clocks, understand the division of time in a more practical sense.