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Convert from Absolute Salinity to Practical Salinity

Source: R/gsw.R
gsw_SP_from_SA.Rd

Calculate Practical Salinity from Absolute Salinity, pressure, longitude, and latitude.

Usage

gsw_SP_from_SA(SA, p, longitude, latitude)

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

longitude

longitude in decimal degrees, positive to the east of Greenwich. (This is called long in the TEOS-10 Matlab code.)

latitude

latitude in decimal degrees, positive to the north of the equator. (This is called lat in the TEOS-10 Matlab code.)

Value

Practical Salinity (PSS-78) [ unitless ]

Details

If SP is a matrix and if its dimensions correspond to the lengths of longitude and latitude, then the latter are converted to analogous matrices with expand.grid.

Note: unlike the corresponding Matlab function, this does not return a flag indicating whether the location is in the ocean.

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_SP_from_SA.html

See also

Other things related to salinity: gsw_C_from_SP(), gsw_SA_from_SP(), gsw_SA_from_SP_Baltic(), gsw_SA_from_Sstar(), gsw_SP_from_C(), gsw_SP_from_SK(), gsw_SP_from_SR(), gsw_SP_from_Sstar(), gsw_SR_from_SP(), gsw_Sstar_from_SA(), gsw_Sstar_from_SP(), gsw_deltaSA_from_SP()

Examples

SA <-   c(34.7118, 34.8915, 35.0256, 34.8472, 34.7366, 34.7324)
p <-    c(     10,      50,     125,     250,     600,    1000)
lat <-  c(      4,       4,       4,       4,       4,       4)
long <- c(    188,     188,     188,     188,     188,     188)
SP <- gsw_SP_from_SA(SA,p,long,lat)
stopifnot(all.equal(SP, c(34.548721553448317, 34.727477488096639, 34.860554877708005,
                          34.680971112271791, 34.567971663653388, 34.560036751118204)))