Dec 13, 2012

Florida's "drought cycle," revealed

Hydrologists often focus on rain,

But understanding drought is equally important in Florida.


 Here's the annual drought
cycle map I made ...

The animated map above shows Florida's median annual atmospheric drought cycle, as based on the Keetch Byram Drought Index (KBDI), over the past ten years. So often I had found myself turning to the Florida Forest Service's county-by-county KBDI map (see below) to get a handle on current drought conditions across the state, but the problem was the it only showed current conditions, thus I was always left scratching my head:

Are the values normal for that time (any time) of year?


Accordingly, I went in and crunched the numbers, fire district by fire district, from 2000 to 2011, and produce the animated map you see above.

What does the map say?

To compliment Florida
Forest Service's daily-

updated map above

Most evident is that drought does not descend equally across all parts of the peninsula, nor at the same time, but there are also interesting wrinkles, too. Over the typical annual cycle, for instance, drought severity peaks the highest (but for a relatively short-lived time, i.e. late spring) in the Big Bend area. Compare that to south Florida where atmospheric drought occurs over a more protracted period, i.e. late fall, winter and most of spring, but at a lower amplitude. The wrinkle for south Florida is that the KBDI is an imperfect index for tracking drought because it doesn't account for the presence or absence of water in its vast wetland mosaic, (i.e. are natural fire breaks flooded or dry?).

Regardless, I still find it interesting to watch both maps unfold.

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