Uncertainty of background roughness and wind resource

A form has been derived to estimate the uncertainty in WAsP’s ‘horizontal extrapolation’ caused by uncertainty in background roughness length (Kelly & Jørgensen, 2016). This includes a generalized power-curve form, which allows translation of mean-wind uncertainty into AEP uncertainty. We also give a useful representation and analysis of roughness-uncertainty associated with both measurement-based and user-assigned roughnesses.