swSigma4 {oce}

Seawater Potential Density Anomaly Referenced to 4000db Pressure

Description

This is analogous to swSigma0(), but referenced to 4000db pressure.

Usage

swSigma4(
  salinity,
  temperature = NULL,
  pressure = NULL,
  longitude = NULL,
  latitude = NULL,
  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, ignoring the other parameters, if they are supplied.

temperature

in-situ temperature (^\circC), 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" (references 1 and 2) or "gsw" (references 3 and 4).

Value

Potential density anomaly (kg/m^3).

Author(s)

Dan Kelley

References

See citations provided in the swRho() documentation.

See Also

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