oce (version 0.9-18)

swRrho: 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".

Value

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

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).

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"))