Feb 8, 2012

Collier County KBDI Cheat Sheet

Meteorological drought is upon us.

All you have to do is look at the KBDI map to know.

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This map updates daily

But how good is a map really if you can't place the current value relative to the statistical framework and historical parade of data that came before?

The images below do just that.


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I'll keep this graph updated weekly.

The above graph shows the rise and fall of the Keech Byram Drought Index (KBDI) for Collier County over the past three years. The black line shows the KBDI value, September 2009 to present.  The color coding, i.e. horizontal layers behind, is identical to the color scheme used on the Florida Forest Service's famous map. The shading, i.e. degree of fading, shows the 11-year historical statistics, 2000 to present, and the dotted white line shows the median value over that period of time.  The lower the KBDI index (blue and green range) the lower the level of meteorologic drought.

The power of this graph is that it paints the point relative to its statistical range.


But what if you want to look back even further?

That’s where the historical calendar comes into play.

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I'll update this calendar weekly, too.

The calendar reads like the pages of a book:

Chronologically by years down and months of the year (from January to December) across. Similar to the graph, it is color coded to match the map.  The thin line of blue and green points indicate periods of regular rain whereas yawning lines of red and purple points indicate times of extreme meteorologic drought.


You've heard of the rug that ties the room together.

The graph and calendar do the same thing for the map.

6 comments:

Robert Sobczak said...

From Sue by email:

"From what weather station is the KBDI measured. We have "issues" with the numbers as they appear to be for inland Collier while we work in Coastal (more rain and/or humidity, therefore should have lower vaules)."

Robert Sobczak said...

Hi Sue,

This is the Collier County wide value provided by the Florida Forest Service (for all 67 counties and 15 districts). They also do a state-wide computation. You're right, it depends on what level you want to look at it. Do you have records for KBDI, or does it apply in your area. That's one issue we have with it in the preserve. KBDI is better suited for land-centric (not wetland centric) watersheds. They still follow it loosely and burn plans are tied to it, thus it's still a useful tool.

Robert Sobczak said...

From Kevin by email:

"Bob your graph is upside down KBDI is a measure of how deep the moisture is in the soil 0 is on the surface and it goes down....."

Robert Sobczak said...

Hi Kevin,

I see what you are saying and I like your idea. I was just plotting the values 1-800 as reported on their records, but environmentally speaking, it being a depth of soil moisture, there is a strong arguement for plotting them the other way around.

Rick said...

It would be very helpful if you read Keech-Byrum's original paper. You will see why this doesn't work well in the sandy and or oolitic substrates of Florida. We have abandoned the use of KBDI at Everglades Fire management because it simply does not work.

Robert Sobczak said...

I agree Rick, the index is land centric and not the best match for wetland predominated areas. It's not a silver bullet but it is factored into the mix.