gsw_sigma4 {gsw}

Potential density anomaly referenced to 4000 dbar

Description

This uses the 75-term density equation, and returns potential density referenced to a pressure of 4000 dbar, minus 1000 kg/m^3.

Usage

gsw_sigma4(SA, CT)

Arguments

SA

Absolute Salinity [ g/kg ]

CT

Conservative Temperature [ degC ]

Value

potential density anomaly with reference pressure 4000 dbar [ kg/m^3 ]

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_sigma4.html

See Also

Other things related to density: gsw_CT_from_rho(), gsw_CT_maxdensity(), gsw_SA_from_rho(), gsw_alpha_on_beta(), gsw_alpha_wrt_t_exact(), gsw_alpha_wrt_t_ice(), gsw_alpha(), gsw_beta_const_t_exact(), gsw_beta(), gsw_pot_rho_t_exact(), gsw_rho_alpha_beta(), gsw_rho_first_derivatives_wrt_enthalpy(), gsw_rho_first_derivatives(), gsw_rho_ice(), gsw_rho_t_exact(), gsw_rho(), gsw_sigma0(), gsw_sigma1(), gsw_sigma2(), gsw_sigma3(), gsw_specvol_alpha_beta(), gsw_specvol_anom_standard(), gsw_specvol_ice(), gsw_specvol_t_exact(), gsw_specvol()

Examples

SA <- c(34.7118, 34.8915, 35.0256, 34.8472, 34.7366, 34.7324)
CT <- c(28.8099, 28.4392, 22.7862, 10.2262,  6.8272,  4.3236)
sigma4 <- gsw_sigma4(SA,CT)
stopifnot(all.equal(sigma4, c(37.900374609834898, 38.166979617032439, 40.280876075282549,
                              43.896091033421953, 44.631677245327637, 45.171817312020039)))