See the example PDF above...
The extension of each bar in the wind rose from ?inner
circle? towards ?outer circle? represents the percentage of the time the wind
blew from those various directions.
The outer circle percentage indicates
the amount of relative uniformity of the wind direction. For example, if
there was a very strange site where the wind only blew from one direction all
the time, and never from any other direction, there would be a single bar going
out from 0 to 100%. Most sites, however, have more scatter with wind
directions distributed among numerous directions.
All of the bars
extending out will of course add up to 100% of the time period that was
measured. The ?outer circle? value is intended to provide some context
for the graph so that at a quick glance, you can tell that at the site below,
almost 30% of the time, the wind direction was southwest, another 25% or so was
north, and then the rest of the directions are distributed among the other
directions to add up to the remaining 45%.