oce (version 1.7-10)

swSigmaT: Seawater quasi-potential density anomaly

Description

Compute \(\sigma_t\), a rough estimate of potential density of seawater, minus 1000 kg/m\(^3\).

Usage

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

Value

Quasi-potential density anomaly (kg/m\(^3\)), defined as the density calculated with pressure set to zero.

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 (\(^\circ\)C), 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).

Author

Dan Kelley

Details

If the first argument is an oce object, then salinity, etc., are extracted from it, and used for the calculation.

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(), swSigma4(), swSigmaTheta(), swSigma(), swSoundAbsorption(), swSoundSpeed(), swSpecificHeat(), swSpice(), swSstar(), swTFreeze(), swTSrho(), swThermalConductivity(), swTheta(), swViscosity(), swZ()

Examples

swSigmaT(35, 13, 1000, longitude=300, latitude=30, eos="gsw") # 26.39623
swSigmaT(35, T90fromT68(13), 1000, eos="unesco") # 26.39354