Converting Ocean Variables

Package workings

This package will convert the variables practical salinity and potential temperature into absolute salinity and conservative temperature. In doing so a pressure variable is needed, so this is created and returned in the RasterStack. A density variable (either in-situ or potential referenced to a user input) is computed and added to the RasterStack. See the example for how the module can be used.

Variables

The variables are named using the symbols that represent them. The symbols are unicode characters which can be generated in the julia repl by pressing tab after the varible

julia> \theta#press tab

will autocomplete to θ, the symbol for potential temperature. The subscript letters that are used to distinguish between practical salinity, Sₚ, and absolute salinity, Sₐ, are also added in the julia repl

julia> S\_a#press tab

Currently the varabile symbols are:

• θ potential temperature
• Θ conservative temperature
• Sₚ practical salinity
• Sₐ absolute salinity
• p pressure
• ρ in-situ seawater density
• σₚ potential density at user defined reference pressure ₚ
• α thermal expansion coefficient
• β haline contraction coefficient.

Limitations

If the required dimensions for the conversions are not present an error will be thrown. For example, trying to convert a RasterStack that has no depth dimension will not work as the Z dimension is not found and the pressure variable depends on depth. There is a manual workaround for this. When defining the RasterStack add the Z dimension as a single entry, rather than a Vector,

lons, lats, z = -180:180, -90:90, 0.0
stack = RasterStack(data, (X(lons), Y(lats), Z(z)))

This is equivalent to a two dimensional RasterStack at sea-surface height (z = 0).

At this stage it is also not possible to slice a Raster then convert it. This is something that will be implemented at some stage. For details on why this is the case see this issue. As the example shows it is straightforward to first convert a Raster and then slice it.

For a full list of the functions in this module see the function index or look at the example to see the module in action.