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First Derivatives of Entropy

Source: R/gsw.R
gsw_entropy_first_derivatives.Rd

First Derivatives of Entropy

Usage

gsw_entropy_first_derivatives(SA, CT)

Arguments

SA

Absolute Salinity [ g/kg ]. The valid range for most `gsw` functions is 0 to 42 g/kg.

CT

Conservative Temperature [ degC ].

Value

a list containing eta_SA [ (J/(kg*degC) / (g/kg) ], the derivative of entropy wrt Absolute Salinity, and eta_CT [ (J/(kg*degC^2) ], the derivative of entropy wrt Conservative Temperature.

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.

References

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

See also

Other things related to entropy: gsw_CT_from_entropy(), gsw_entropy_from_pt(), gsw_entropy_from_t(), gsw_entropy_ice(), gsw_pt_from_entropy()

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)
d <- gsw_entropy_first_derivatives(SA, CT)
stopifnot(all.equal(d$eta_SA, c(-0.263286800711655, -0.263977276574528, -0.255367497912925,
                                -0.238066586439561, -0.234438260606436, -0.232820684341694)))
stopifnot(all.equal(d$eta_CT, c(13.221031210083824, 13.236911191313675, 13.489004628681361,
                                14.086599016583795, 14.257729576432077, 14.386429945649411)))