three reanalysis products over the period of January 1997 through December 2017:

-   Version 2 of the Modern-Era Retrospective analysis for Research and Applications (MERRA-2, @gelaro2017modern). We specifically use the M2T1NXSLV data product, which provides diagnostic wind speed at 50 m above ground level (AGL), interpolated from the lowest model level output (on average about 32 m AGL), using Monin Obukhov similarity theory. Data are provided at an hourly time resolution.

-   The European Reanalysis Interim (ERA-Interim) data set [@dee2011era]. We specifically use output at the 58$^\text{th}$ model level, which on average corresponds to a height of about 72 m AGL. Data are provided at a 6-hourly time resolution.

-   The National Centers for Environmental Prediction v2 (NCEP-2) data set [@saha2014ncep]. We specifically use diagnostic wind speed data at 10 m AGL. Data are provided at a 6-hourly time resolution.

The wind speed data are density-corrected at their native time resolutions to correlate more strongly with wind plant power production (i.e., higher-density air in winter produces more power than lower-density air in summer, wind speed being the same): $$U_{\text{dens,corr}} = U \left(\frac{\rho}{\rho_{\text{mean}}} \right) ^{1/3}
    \label{den_corr}$$ where $U_{\text{dens,corr}}$ is the density-corrected wind speed, $U$ is the wind speed, $\rho$ is air 