R: Absolute Salinity Anomaly Ratio

gsw_SAAR {gsw} | R Documentation

## Absolute Salinity Anomaly Ratio

### Description

Absolute Salinity Anomaly Ratio

### Usage

    gsw_SAAR(p, longitude, latitude)

### Arguments

`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.)

### Details

The present R function works with a wrapper to a C function contained within the GSW-C system (Version 3.05-4 dated 2017-08-07, available at https://github.com/TEOS-10/GSW-C, as git commit '5b4d959e54031f9e972f3e863f63e67fa4f5bfec'), which stems from the GSW-Fortran system (https://github.com/TEOS-10/GSW-Fortran) which in turn stems from the GSW-Matlab system (https://github.com/TEOS-10/GSW-Matlab). Consult http://www.teos-10.org to learn more about these software systems, their authorships, and the science behind it all.

### Value

a list containing `SAAR`, which is the (unitless) Absolute Salinity Anomality Ratio, and `in_ocean` is set to 1 if `SAAR` is nonzero, or to 0 otherwise.

### Bugs

The definition of `in_ocean` is incorrect, because the C function named `gsw_saar`, which is called by the present R function, does not calculate `in_ocean`, as the base Matlab function named `gsw_SAAR` does. However, examination of the Matlab code shows that `in_ocean` is set to 0 along with `SAAR`, whenever the original estimate of the latter is nonfinite. Thus, points that would be siganlled as being on the land by the Matlab code are indicated in the same way with the present R function. However, other points may also be indicated as being on land, if `SAAR` is simply zero in the first calculation. Whether this poses a problem in practice is an open question, since it seems likely that this function would only be called with oceanic locations, anyway. If problems arise for users, a patch can be written to improve things.

### References

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

### Examples

    p <- c(10, 50, 125, 250, 600, 1000)
    longitude <- c(188, 188, 188, 188, 188, 188)
    latitude <- c(4, 4, 4, 4, 4, 4)
    SAAR <- gsw_SAAR(p, longitude, latitude)
    expect_equal(1e3*SAAR$SAAR, c(0.004794295602143, 0.007668755837570, 0.018919828449091,
                                  0.077293264028981, 0.161974583039298, 0.270652408428964))
    expect_equal(SAAR$in_ocean, rep(1, 6))

[Package gsw version 1.0-5 Index]