Thanks 'rnzoli', I shall have a look at that. 117 pages will take me a while !
I understand what you mean about the difficulty of identifying what is causing specific turbulence - I have flown both sailplanes and tug aircraft into wave conditions frequently; the turbulence conditions at low level can vary greatly during a single day, or some days from one tow to the next.
In the case of the windfarm nearby us, we have from time to time encountered notable turbulence while climbing out downwind of the windfarm in wind directions varying from West through SW to due South, which suggests to me that the most likely cause is blade turbulence from the windfarm. It is variable and unpredictable, sometimes completely absent when anticipated and then occasionally surprisingly strong. I suspect that atmospheric conditions influence its propagation and likely 'longevity' downwind, just as with other effects, like wave. I know one pilot who reported being rolled rapidly through more than 90 degrees flying just downwind of the farm, which must have been exciting. I don't know how close that aeroplane was.
For the airfield case described in the accident report, I'd have thought ground interference would rapidly diminish or decay the rotor, though I think wing wake rotors can last for quite a long time and track a fairly long way. Interesting.