8.7 SIGMA COORDINATE DATA
With sigma coordinate data the vertical coordinate (or layer thickness) is available as a dependent variable and the Z axis of the sigma-encoded variables is layer number (the Z index). This is precisely analogous to method 3 of handling collections of profiles. The family of ZAXREPLACE functions may be used to regrid this kind of data to a Z axis with physical units.
See also the FAQ on Using Sigma Coordinates.
8.7.1 Visualization techniques for sigma coordinate data
Visualizations of sigma coordinate data in vertical section planes are best handled with the 3-argument versions of the SHADE, FILL, CONTOUR and VECTOR commands. See further information in Customizing Plots.
For visualization of sigma coordinate data in other planes or orientations use the techniques described in the next section.
8.7.2 Analysis techniques for sigma coordinate data
Analysis of sigma coordinate data, which requires shifting to depth or pressure coordinates, is facilitated by the function ZAXREPLACE, which converts from layer number to other vertical coordinate axes. See sigma_coordinate_demo.jnl for an example. If the data set provides layer thickness rather than depth a depth variable may be created using integration with @iin.