First Derivatives of Conservative Temperature for Freezing Water

gsw_CT_freezing_first_derivatives(SA, p, saturation_fraction = 1)

Arguments

SA: Absolute Salinity [ g/kg ]
p: sea pressure [dbar], i.e. absolute pressure [dbar] minus 10.1325 dbar
saturation_fraction: fraction of air in water [unitless]

Value

A list containing CTfreezing_SA [ K/(g/kg) ], the derivative of Conservative Temperature with respect to Absolute Salinity at constant potential temperature, and CTfreezing_p [ unitless], the derivative of Conservative Temperature with respect to pressure at constant Absolute Salinity.

Implementation Note

This R function uses a wrapper to a C function contained within the GSW-C system as updated 2021-12-28 at https://github.com/TEOS-10/GSW-C with git commit `98f0fd40dd9ceb0ba82c9d47ac750e935a7d0459`.

The C function uses data from the library/gsw_data_v3_0.mat file provided in the GSW-Matlab source code, version 3.06-11. Unfortunately, this version of the mat file is no longer displayed on the TEOS-10.org website. Therefore, in the interests of making GSW-R be self-contained, a copy was downloaded from http://www.teos-10.org/software/gsw_matlab_v3_06_11.zip on 2022-05-25, the .mat file was stored in the developer/create_data directory of https://github.com/TEOS-10/GSW-R, and then the dataset used in GSW-R was created based on that .mat file.

Please consult http://www.teos-10.org to learn more about the various TEOS-10 software systems.

References

http://www.teos-10.org/pubs/gsw/html/gsw_CT_freezing_first_derivatives.html

Examples

SA <- c(                 34.7118, 34.8915, 35.0256, 34.8472, 34.7366, 34.7324)
p <- c(                       10,      50,     125,     250,     600,    1000)
saturation_fraction <- c(      1,     0.8,     0.6,     0.5,     0.4,       0)
r <- gsw_CT_freezing_first_derivatives(SA, p, saturation_fraction)
stopifnot(all.equal(r$CTfreezing_SA,
    c(-0.058193253897272, -0.058265158334170, -0.058345661671901,
     -0.058373842446463, -0.058534544740846, -0.058730846361252)))
stopifnot(all.equal(r$CTfreezing_p/1e-7,
    c(-0.765300390432684, -0.766942996466485, -0.769892679988284,
      -0.774561011527902, -0.787769143040504, -0.802771548245855)))