Compute \(\sigma_t\), a rough estimate of potential density of seawater, minus 1000 kg/m\(^3\).
swSigmaT(
salinity,
temperature = NULL,
pressure = NULL,
longitude = NULL,
latitude = NULL,
eos = getOption("oceEOS", default = "gsw")
)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.
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 (dbar)
longitude of observation (only used if eos="gsw";
see “Details”).
latitude of observation (only used if eos="gsw"; see
“Details”).
equation of state, either "unesco" (references 1 and 2)
or "gsw" (references 3 and 4).
Quasi-potential density anomaly (kg/m\(^3\)), defined as the density calculated with pressure set to zero.
If the first argument is an oce object, then salinity, etc., are extracted from it, and used for the calculation.
See citations provided in the swRho() documentation.
Other functions that calculate seawater properties:
T68fromT90(),
T90fromT48(),
T90fromT68(),
computableWaterProperties(),
locationForGsw(),
swAbsoluteSalinity(),
swAlpha(),
swAlphaOverBeta(),
swBeta(),
swCSTp(),
swConservativeTemperature(),
swDepth(),
swDynamicHeight(),
swLapseRate(),
swN2(),
swPressure(),
swRho(),
swRrho(),
swSCTp(),
swSR(),
swSTrho(),
swSigma(),
swSigma0(),
swSigma1(),
swSigma2(),
swSigma3(),
swSigma4(),
swSigmaTheta(),
swSoundAbsorption(),
swSoundSpeed(),
swSpecificHeat(),
swSpice(),
swSpiciness0(),
swSpiciness1(),
swSpiciness2(),
swSstar(),
swTFreeze(),
swTSrho(),
swThermalConductivity(),
swTheta(),
swViscosity(),
swZ()
swSigmaT(35, 13, 1000, longitude = 300, latitude = 30, eos = "gsw") # 26.39623
#> [1] 26.39623
swSigmaT(35, T90fromT68(13), 1000, eos = "unesco") # 26.39354
#> [1] 26.39354