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oce (version 0.9-20)

swSigma3: Seawater potential density anomaly referenced to 3000db pressure

Description

Compute $sigma$, the potential density of seawater (minus 1000 kg/m$^3$), referenced to 3000db pressure.

Usage

swSigma3(salinity, temperature = NULL, pressure = NULL, longitude = 300, latitude = 30, 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.
temperature
in-situ temperature [$deg$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" [1,2] or "gsw" [3,4].

Value

Potential density anomaly [kg/m$^3$].

Details

Definition: $sigma_1=sigma_theta=rho(S,theta(S,t,p),3000)$ - 1000 kg/m$^3$.

References

See citations provided in the swRho documentation.

See Also

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