swRho {oce} | R Documentation

## Seawater density

### Description

Compute rho, the in-situ density of seawater.

### Usage

    swRho(salinity, temperature=NULL, pressure=NULL,
        longitude, latitude, eos=getOption("oceEOS", default="gsw"))

### Arguments

`salinity` | either practical salinity (in which case `temperature` and `pressure` must be provided) or an `oce` object, in which case `salinity`, `temperature` (in the ITS-90 scale; see next item), etc. are inferred from the object.

`temperature`

in-situ temperature [degC], defined on the ITS-90 scale. This scale is used by GSW-style calculation (as requested by setting `eos="gsw"`), and is the value contained within `ctd` objects (and probably most other objects created with data acquired in the past decade or two). Since the UNESCO-style calculation is based on IPTS-68, the temperature is converted within the present function, using `T68fromT90`.

`pressure` | pressure [dbar]
`longitude` | longitude of observation (only used if `eos="gsw"`; see ‘Details’).
`latitude` | latitude of observation (only used if `eos="gsw"`; see ‘Details’).
`eos` | equation of state, either `"unesco"` [1,2] or `"gsw"` [3,4].

### Details

If the first argument is an `oce` object, then values for salinity, etc., are extracted from it, and used for the calculation, and the corresponding arguments to the present function are ignored.

If `eos="unesco"`, the density is calculated using the UNESCO equation of state for seawater [1,2], and if `eos="gsw"`, the GSW formulation [3,4] is used.

### Value

In-situ density [kg/m^3].

### Temperature units

The UNESCO formulae are defined in terms of temperature measured on the IPTS-68 scale, whereas the replacement GSW formulae are based on the ITS-90 scale. Prior to the addition of GSW capabilities, the various `sw*` functions took temperature to be in IPTS-68 units. As GSW capabilities were added in early 2015, the assumed unit of `temperature` was taken to be ITS-90. This change means that old code has to be modified, by replacing e.g. `swRho(S, T, p)` with `swRho(S, T90fromT68(T), p)`. At typical oceanic values, the difference between the two scales is a few millidegrees.

### Author(s)

Dan Kelley

### References

[1] Fofonoff, P. and R. C. Millard Jr, 1983. Algorithms for computation of fundamental properties of seawater. Unesco Technical Papers in Marine Science, 44, 53 pp

[2] Gill, A.E., 1982. Atmosphere-ocean Dynamics, Academic Press, New York, 662 pp.

[3] IOC, SCOR, and IAPSO (2010). The international thermodynamic equation of seawater-2010: Calculation and use of thermodynamic properties. Technical Report 56, Intergovernmental Oceanographic Commission, Manuals and Guide.

[4] McDougall, T.J. and P.M. Barker, 2011: Getting started with TEOS-10 and the Gibbs Seawater (GSW) Oceanographic Toolbox, 28pp., SCOR/IAPSO WG127, ISBN 978-0-646-55621-5.

### See Also

Related density routines include `swSigma0` (and equivalents at other pressure horizons), `swSigmaT`, and `swSigmaTheta`.

### Examples

    library(oce)
    rho <- swRho(35, 13, 1000)

[Package oce version 0.9-18 Index]