Sep 11, 2013

Tail that wags the water cycle

We're all familiar with "the tail that wags the dog,"

But did you know a similar phrase also applies to south Florida hydrology, too?

The above graph shows the frequency distribution of south Florida wide daily precipitation from 1992 to present.  Far an away the most frequent weather occurrence is our No Rain Days, i.e. less than 0.05 inches.  Most of the rest of the distribution curve is comprised by intermediate rains in which between 0.05 and 1 inch of rain on average fell across south Florida.  The tail at the end (highlighted in yellow) are the pivotal (yet rare) Big Rain Days.  They are surprisingly conspicuous by their absence, too.   

It's called the tail that wags the water cycle.

As you can see from the frequency distribution graph above, the tail are our Big Rain Days (BRDs).  Big Rain Days are from a time-wise perspective only a very minuscule portion of our total water year -- for instance this year we've had only four -- but their impact on the hydrograph can be quite pronounced for weeks and months to come.

They can also be conspicuous by their absence, too:

A term that pops up if for too long they they go missing is called drought.

South Florida's hydrograph both rises and falls by the presence and absence of the tail.

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