R: Density ratio

swRrho {oce} | R Documentation

## Density ratio

### Description

Compute density ratio

### Usage

    swRrho(ctd, sense = c("diffusive", "finger"), smoothingLength = 10, df,
      eos = getOption("oceEOS", default = "gsw"))

### Arguments

`ctd` | an object of class `ctd`
`sense` | an indication of the sense of double diffusion under study and therefore of the definition of Rrho; see ‘Details’
`smoothingLength` | ignored if `df` supplied, but otherwise the latter is calculated as the number of data points, divided by the number within a depth interval of `smoothingLength` metres.
`df` | if given, this is provided to `smooth.spline`.
`eos` | equation of state, either `"unesco"` or `"gsw"`.

### Details

This computes Rrho (density ratio) from a `ctd` object.

If `eos="unesco"`, this is done by calculating salinity and potential-temperature derivatives from smoothing splines whose properties are governed by `smoothingLength` or `df`. If `sense="diffusive"` the definition is (beta*dS/dz)/(alpha*d(theta)/dz) and the reciprocal for `"finger"`.

If `eos="gsw"`, this is done by extracting absolute salinity and conservative temperature, smoothing with a smoothing spline as in the `"unesco"` case, and then calling `gsw_Turner_Rsubrho` on these smoothed fields. Since the gsw function works on mid-point pressures, `approx` is used to interpolate back to the original pressures.

If the default arguments are acceptable, `ctd[["Rrho"]]` may be used instead of `swRrho(ctd)`.

### Value

Density ratio defined in either the `"diffusive"` or `"finger"` sense.

### Author(s)

Dan Kelley and Chantelle Layton

### See Also

Other functions that calculate seawater properties: `T68fromT90`, `T90fromT48`, `T90fromT68`, `swAbsoluteSalinity`, `swAlphaOverBeta`, `swAlpha`, `swBeta`, `swCSTp`, `swConservativeTemperature`, `swDepth`, `swDynamicHeight`, `swLapseRate`, `swN2`, `swPressure`, `swRho`, `swSCTp`, `swSTrho`, `swSigma0`, `swSigma1`, `swSigma2`, `swSigma3`, `swSigma4`, `swSigmaTheta`, `swSigmaT`, `swSigma`, `swSoundAbsorption`, `swSoundSpeed`, `swSpecificHeat`, `swSpice`, `swTFreeze`, `swTSrho`, `swThermalConductivity`, `swTheta`, `swViscosity`, `swZ`

### Examples

    library(oce)
    data(ctd)
    u <- swRrho(ctd, eos="unesco")
    g <- swRrho(ctd, eos="gsw")
    p <- ctd[["p"]]
    plot(u, p, ylim=rev(range(p)), type='l', xlab=expression(R[rho]))
    lines(g, p, lty=2, col='red')
    legend("topright", lty=1:2, legend=c("unesco", "gsw"), col=c("black", "red"))

[Package oce version 0.9-20 Index]