| Wind Frequency Rose Difference | |
The wind rose frequency difference is a number that indicates the degree of difference between two wind frequency roses. From simple visual inspection one can see the similarity between the two wind frequency roses shown in the graph below:
But we wish to define a numerical metric to indicate precisely how similar are those two roses. We do so by calculating in every direction sector the absolute value of the difference between the two frequencies, and then finding the sum of those differences:
where: | ||
| DWR | is the wind frequency rose difference [%] | |
| fa,i | is the frequency the wind blows from sector i in frequency rose a [%] | |
| fb,i | is the frequency the wind blows from sector i in frequency rose b [%] | |
| N | is the number of direction sectors |
The wind frequency roses in the graph above yield a total difference of 14.94%:
| Sector | Frequency (%) | |||
|---|---|---|---|---|
| # | Midpoint | Onsite | Reference | Difference |
| 1 | 0° | 13.72 | 11.65 | 2.07 |
| 2 | 30° | 6.14 | 5.27 | 0.87 |
| 3 | 60° | 3.08 | 3.12 | 0.04 |
| 4 | 90° | 2.10 | 3.17 | 1.07 |
| 5 | 120° | 3.20 | 4.29 | 1.09 |
| 6 | 150° | 9.57 | 8.75 | 0.82 |
| 7 | 180° | 15.88 | 14.97 | 0.91 |
| 8 | 210° | 13.90 | 16.00 | 2.10 |
| 9 | 240° | 7.98 | 11.16 | 3.17 |
| 10 | 270° | 7.47 | 6.84 | 0.63 |
| 11 | 300° | 6.83 | 5.58 | 1.25 |
| 12 | 330° | 10.11 | 9.20 | 0.91 |
| Total | 100.00 | 100.00 | 14.94 | |
See also