gsw_CT_freezing_first_derivatives_poly function

First Derivatives of Conservative Temperature for Freezing Water (Polynomial version)

gsw_CT_freezing_first_derivatives_poly(SA, p, saturation_fraction = 1)

Arguments

• SA: Absolute Salinity [ g/kg ]. The valid range for most gsw functions is 0 to 42 g/kg.
• p: sea pressure [dbar], i.e. absolute pressure [dbar] minus 10.1325 dbar
• saturation_fraction: fraction of air in water [unitless]

Returns

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 2022-10-11 at https://github.com/TEOS-10/GSW-C with git commit 657216dd4f5ea079b5f0e021a4163e2d26893371.

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.

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_poly(SA, p, saturation_fraction)
stopifnot(all.equal(r$CTfreezing_SA,
    c(-0.058191181082769, -0.058263310660779, -0.058343573188907,
     -0.058370514075271, -0.058528023214462, -0.058722959729433)))
stopifnot(all.equal(r$CTfreezing_p/1e-7,
    c(-0.765690732336706, -0.767310677213890, -0.770224214219328,
     -0.774843488962665, -0.787930403016584, -0.802821704643775)))

References

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