polaris.tasks.ocean.horiz_press_grad.eos_expansion.edge_expansion

polaris.tasks.ocean.horiz_press_grad.eos_expansion.edge_expansion(temperature: DataArray, salinity: DataArray, pressure: DataArray) → Dataset

The edge-shared expansion of [edge-ref]: the four coefficients and the reference state, each averaged over the two cells of the edge.

Parameters:

• temperature (xarray.DataArray) – Layer-mean conservative temperature in degC, with an nCells dimension of size 2.

• salinity (xarray.DataArray) – Layer-mean absolute salinity in g kg-1, on the same points.

• pressure (xarray.DataArray) – Layer-mean sea gauge pressure in Pa (PressureMid), on the same points.

Returns:

expansion (xarray.Dataset) – alpha_0, alpha_theta, alpha_s, alpha_p and the reference state theta_ref, s_ref, p_ref, with nCells contracted away by the edge average.

Note that alpha_0 is the average of the two cells’ specific volumes, each evaluated at its own state – not specific volume evaluated at the averaged state. The difference is second order in the cross-edge contrast, and is exactly what source 4 of the remainder accounts for.