oce (version 1.1-1)

swTheta: Seawater potential temperature

Description

Compute the potential temperature of seawater, denoted \(\theta\) in the UNESCO system, and pt in the GSW system.

Usage

swTheta(salinity, temperature = NULL, pressure = NULL,
  referencePressure = 0, longitude = NULL, latitude = NULL,
  eos = getOption("oceEOS", default = "gsw"))

Arguments

salinity

either salinity [PSU] (in which case temperature and pressure must be provided) or an oce object (in which case salinity, etc. are inferred from the object).

temperature

in-situ temperature [\(^\circ\)C], defined on the ITS-90 scale; see “Temperature units” in the documentation for swRho, and the examples below.

pressure

pressure [dbar]

referencePressure

reference 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 temperature [\(^\circ\)C] of seawater, referenced to pressure referencePressure.

Details

Different formulae are used depending on the equation of state. If eos is "unesco", the method of Fofonoff et al. (1983) is used [1,2]. Otherwise, swTheta uses gsw_pt_from_t from the gsw package.

If the first argument is a ctd or section object, then values for salinity, etc., are extracted from it, and used for the calculation, and the corresponding arguments to the present function are ignored.

References

[1] Fofonoff, P. and R. C. Millard Jr, 1983. Algorithms for computation of fundamental properties of seawater. Unesco Technical Papers in Marine Science, 44, 53 pp

[2] Gill, A.E., 1982. Atmosphere-ocean Dynamics, Academic Press, New York, 662 pp.

[3] IOC, SCOR, and IAPSO (2010). The international thermodynamic equation of seawater-2010: Calculation and use of thermodynamic properties. Technical Report 56, Intergovernmental Oceanographic Commission, Manuals and Guide.

[4] McDougall, T.J. and P.M. Barker, 2011: Getting started with TEOS-10 and the Gibbs Seawater (GSW) Oceanographic Toolbox, 28pp., SCOR/IAPSO WG127, ISBN 978-0-646-55621-5.

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, swSigma3, swSigma4, swSigmaTheta, swSigmaT, swSigma, swSoundAbsorption, swSoundSpeed, swSpecificHeat, swSpice, swTFreeze, swTSrho, swThermalConductivity, swViscosity, swZ

Examples

# NOT RUN {
library(oce)
## test value from Fofonoff et al., 1983
expect_equal(36.8818748026, swTheta(40, T90fromT68(40), 10000, 0, eos="unesco"))

# Example from a cross-Atlantic section
data(section)
stn <- section[['station', 70]]
plotProfile(stn, 'theta', ylim=c(6000, 1000))
lines(stn[['temperature']], stn[['pressure']], lty=2)
legend("bottomright", lty=1:2,
       legend=c("potential", "in-situ"),
       bg='white', title="Station 70")

# }