polaris.ocean.vertical.sigma.init_sigma_vertical_coord

polaris.ocean.vertical.sigma.init_sigma_vertical_coord(config, ds)[source]

Create a sigma (terrain-following) vertical coordinate based on the config options in the vertical_grid` section and the bottomDepth and ssh variables of the mesh data set.

The following new variables will be added to the data set:

  • minLevelCell - the index of the top valid layer

  • maxLevelCell - the index of the bottom valid layer

  • cellMask - a mask of where cells are valid

  • layerThickness - the thickness of each layer

  • restingThickness - the thickness of each layer stretched as if ssh = 0

  • zMid - the elevation of the midpoint of each layer

The sigma coordinate makes use of a 1D reference vertical grid. The following variables associated with that field are also added to the mesh:

  • refTopDepth - the positive-down depth of the top of each ref. level

  • refZMid - the positive-down depth of the middle of each ref. level

  • refBottomDepth - the positive-down depth of the bottom of each ref. level

  • refInterfaces - the positive-down depth of the interfaces between ref. levels (with nVertLevels + 1 elements).

  • vertCoordMovementWeights - the weights (all ones) for coordinate movement

There is considerable redundancy between these variables but each is sometimes convenient.

Parameters:

  • config (polaris.config.PolarisConfigParser) – Configuration options with parameters used to construct the vertical grid

  • ds (xarray.Dataset) – A data set containing bottomDepth and ssh variables used to construct the vertical coordinate