I decided to show something useful instead of waiting until perfect data is available.
Frequency plot of wind speed over the whole of the UK. The characteristic is logarithmic.
There are data problems, ignore this please.
The Met Office in common with all national meteorological services continue to use cup anemometers rather than eg. ultrasonic This is the advice from WMO (World Meteorological Organisation) specifically to maintain continuity of data for climatic purposes since there are significant differences between cup and other types.
You will notice the law fails at low and high speeds.
The low is about instruments having a low limit on proportionality and about low speed aerodynamics, the way air behaves.
At high speeds the cause is less clear but I am sure it is primarily about the over-speed problem of cup anemometers combined with the growing depth of boundary layer turbulence.
The over-speed is caused by a difference in the acceleration and deceleration rate under non-steady wind conditions, where there is a tendency to over-read. A further problem is when the wind alignment is not horizontal, as happens in turbulence. There are many papers on these kinds of effect.
Very high wind speeds are under-represented. Under severe storm weather stations tend to fail, either instrument damage or often communication failure. I suspect this has no material effect on the result.
Wind power generation
Power generators generally start producing at about 10 mph, reach rated output at about 30 mph and shut down at some point higher than that.
The sites chosen have high wind speeds but the law will be the law.
Image from and annotation with mph conversion
Using meteorological wind data to estimate turbine generation output: a sensitivity analysis
M. L. Kubik 1,* , P. J. Coker 2 , C. Hunt 3
This agrees with what I remembered as typical figures.
Given the logarithmic wind speed frequency it is obvious why wind turbines operate at a small fraction of their maximum rating for most of the time.
Gust speed also follows a log law.
1. To the best of my knowledge.
A problem was identified with the supplied data. After extensive investigation here a support ticket was raised during January. Support have now escalated the matter.
Hopefully when the problem is fixed I will be able to get replacement correct data and post again showing the real thing.
Give them time.
Met Office do not provide access to archived data (at BADC) except for formal academic work, why I am creating an archive here.
The plot is minimising visible effect, there are missing points.
This paper is useful. A great deal of literature exists.
Intercomparison of cup anemometer and sonic anemometers on site at Uccle/Belgium
Luis Gonz´ alez Sotelino, Nicolas De Coster, Peter Beirinckx, Pieter Peeters
Royal Meteorological Institute of Belgium
Post by Tim