| swTheta {oce} | R Documentation |
Compute theta, the potential temperature of seawater.
swTheta(salinity, temperature = NULL, pressure = NULL,
referencePressure = 0, longitude = 300, latitude = 30,
eos = getOption("oceEOS", default = "gsw"))
salinity |
either salinity [PSU] (in which case |
temperature |
in-situ temperature [degC], defined
on the ITS-90 scale; see “Temperature units” in the documentation for
|
pressure |
pressure [dbar] |
referencePressure |
reference pressure [dbar] |
longitude |
longitude of observation (only used if |
latitude |
latitude of observation (only used if |
eos |
equation of state, either |
The potential temperature is defined to be the temperature that a water
parcel of salinity S, in-situ temperature t and
pressure p would have if were to be moved adiabatically to a location
with pressure referencePressure. This quantity is commonly denoted
theta in the oceanographic literature.
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.
For eos="unesco" the method of Fofonoff et al. (1983), is used
[1,2]. For eos="gsw", gsw_pt_from_t is used
[3,4].
Potential temperature [degC] of seawater.
Dan Kelley
[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.
The corresponding potential density anomaly
sigma-theta can be calculated with
swSigmaTheta.
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
library(oce)
print(swTheta(40, T90fromT68(40), 10000, 0, eos="unesco")) # 36.89073 (Fofonoff et al., 1983)
# Demonstrate that the UNESCO and GSW methods agree to a about 0.1C over a
# typical span of values.
S <- c(30,35,30,35)
T <- c(-2,-2,30,30)
p <- 1000 * runif(n=4)
print(max(abs(swTheta(S,T90fromT68(T),p) - swTheta(S,T,p,0,eos="gsw"))))
# 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("topleft", lty=1:2,
legend=c("potential", "in-situ"),
bg='white', title="Station 70")