2.1.2 Wind
The wind used for this study is a climatology computed from the CFSR, the same wind used to force the HyCOM simulations described in 2.1.1. This reanalysis is a fully coupled model representing the interaction between the atmosphere, oceans, land, and sea ice, described by Saha et al. (2010). The CFSR assimilates in situ and satellite observations using sigma–pressure hybrid vertical coordinates, a simplified Arakawa–Schubert convection scheme with momentum mixing (Hong & Pan, 1996, 1998; Pan & Wu, 1995), and orographic gravity wave drag (Alpert et al., 1988, 1996; Young-Joon Kim & Arakawa, 1995). The land surface model is based on the two-layer OSU land model (H. L. Pan & Mahrt, 1987), the SW radiation is parameterized following the NASA approach (Chou et al., 1998; Hou et al., 2002), and the LW radiation following the GFDL approach (Fels & Schwarzkopf, 1975; Schwarzkopf & Fels, 1991), based on the RRTM developed at AER (Taubman et al., 1997). CFSR is coupled to a four-layer Noah land surface model (Ek et al., 2003) and a two-layer sea ice model (Wu et al., 2005). The temporal data resolution is 1 hour, with a spatial resolution of 0.5°. We used the zonal (u -component) and meridional (v -component) wind 10 m above the surface from the CFSRv1 and CFSRv2 reanalysis data. To ensure consistency, we also calculated daily means for the wind data and interpolated them onto the current data grid to create the 25-year climatology. For interpolation, we employed the Modified Akima cubic Hermite interpolation method. This approach utilizes a piecewise function of polynomials, with a maximum degree of three, to interpolate the values of neighboring grid points in each dimension. Specifically, the method employs local data information to generate a continuous curve that passes through the given data points while minimizing the curvature in the resulting interpolated function.