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Background

I am trying to estimate wind speeds at a proposed wind farm site using the method described in this paper hyperlink here. The approach is summarized in figure 2 of the paper.

Short Summary, you get ERA5 reanalysis data, then you scale it relative to wind speed figures calculated in a microscale model (Global Wind Atlas) using a bunch of formulas.

What I've done

  • I have downloaded 12 months of historic hourly ERA5 reanalysis data.
  • I've taken hourly 100m wind speed readings from the 4 neighboring grid points near my site
  • I've used bilinear interpolation to estimate wind speed at site.
  • I've used wind_stats (hyperlink here to get the site specific Generalized Wind Climate (gwc) file from the Global Wind Atlas. to use for statistical downscaling purposes.

But this is where I get stuck

What I've having trouble with

I am having two issues with the gwc file that I am unsure on how to resolve.

  1. The gwc file provides the Weibull A & K parameters at a sector level (i.e. in 30 degree increments up to 360 degree, sort of in a wind rose format). Do I aggregate the sector figures up (if so, how?) or do I do I transform my ERA5 data into sectors then apply the downscaling formulas at that level?
  2. The gwc file doesn't give me a site specific roughness figure, instead it gives me 5 different values. how do I know which roughness figure to use? Do I need a different source of data to first determine what site roughness is?

Help Requested

Does anyone have any experience with the gwc file format? Any assistance be greatly appreciated.

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