Density Ratio

Compute density ratio for a ctd object. An error (perhaps with some hints) is issued for any other type of object.

Usage

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

Arguments

ctd: an oce object that holds salinity, temperature, and pressure. If eos is "gsw", then it must also hold longitude and latitude.
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".
debug: an integer specifying whether debugging information is to be printed during the processing. This is a general parameter that is used by many oce functions. Generally, setting debug=0 turns off the printing, while higher values suggest that more information be printed. If one function calls another, it usually reduces the value of debug first, so that a user can often obtain deeper debugging by specifying higher debug values.

Value

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

Details

If eos="unesco", the work 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", the work is done by extracting absolute salinity and conservative temperature, smoothing with a smoothing spline as in the "unesco" case, and then calling gsw::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).

Other functions that calculate seawater properties: T68fromT90(), T90fromT48(), T90fromT68(), computableWaterProperties(), locationForGsw(), swAbsoluteSalinity(), swAlpha(), swAlphaOverBeta(), swBeta(), swCSTp(), swConservativeTemperature(), swDepth(), swDynamicHeight(), swLapseRate(), swN2(), swPressure(), swRho(), swSCTp(), swSR(), swSTrho(), swSigma(), swSigma0(), swSigma1(), swSigma2(), swSigma3(), swSigma4(), swSigmaT(), swSigmaTheta(), swSoundAbsorption(), swSoundSpeed(), swSpecificHeat(), swSpice(), swSpiciness0(), swSpiciness1(), swSpiciness2(), swSstar(), swTFreeze(), swTSrho(), swThermalConductivity(), swTheta(), swViscosity(), swZ()

Author

Dan Kelley and Chantelle Layton

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"))