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We present a suite of large-eddy simulations of a wind farm operating inconventionally neutral atmospheric boundary layers (CNBLs). A fixed 1.6 GW windfarm is considered for 40 different atmospheric stratification conditions toinvestigate effects on wind-farm efficiency and blockage, as well as relatedgravity-wave excitation. A tuned Rayleigh damping layer and a wave-free fringeregion method (Lanzilao & Meyers, Bound. Layer Meteor. 186, 2023) are used toavoid spurious excitation of gravity waves, and a domain-size study is includedto evaluate and minimize effects of artificial domain blockage. A fully neutralreference case is also considered, to distinguish between a case withhydrodynamic blockage only, and cases that include hydrostatic blockage excitedby gravity waves. We discuss in detail the dependence of gravity-waveexcitation, flow fields, and wind-farm blockage on capping-inversion height,strength and free-atmosphere lapse rate. In all cases, an unfavourable pressuregradient is present in front of the farm, and a favourable pressure gradient inthe farm, with hydrostatic contributions arising from gravity waves at least anorder of magnitude larger than hydrodynamic effects. Using respectivelynon-local and wake efficiencies $\eta_\textit{nl}$ and $\eta_\textit{w}$(Allaerts & Meyers, Bound. Layer Meteor. 166, 2018), we observe a strongnegative correlation between unfavourable upstream pressure rise and$\eta_\textit{nl}$, and a strong positive correlation between the favourablepressure drop in the farm and $\eta_\textit{w}$. Using a simplified lineargravity-wave model, we formulate a simple scaling for$\eta_\textit{nl}/\eta_\textit{w}$, which matches reasonably well with the LESresults.

A parametric large-eddy simulation study of wind-farm blockage and gravity waves in conventionally neutral boundary layers