Hellmann’s exponent (alpha)

[infinity77]

Thank you for this great piece of work, I took some inspiration from your R code to do some analysis in Python using the MERRA data.

One thing that is a bit unclear to me: looking at your function “extrapolate_power_law” in the “VWF.EXTRAPOLATE.R” module - and using MERRA data for Denmark, for example, I find quite a few (about 10%) occurrences where the Hellmann’s exponent is way bigger than the “accepted” values in the literature (usually its maximum value is around 0.6), while I can easily find occurrences where it reaches values of 2.3, particularly in low wind speed conditions.

Do you have a suggestion on how to handle this “inconsistency” - beside saying “forget about it and use the value you get from the linear least squares”?

Thank you in advance for your suggestions.

Andrea.