| swTFreeze {oce} | R Documentation |
Compute in-situ freezing temperature of seawater, using either the UNESCO formulation
(computed as in Section 5 of reference 1) or the GSW formulation (computed
by using gsw::gsw_SA_from_SP() to get Absolute Salinity, and
then gsw::gsw_t_freezing() to get the freezing temperature).
swTFreeze(
salinity,
pressure = NULL,
longitude = NULL,
latitude = NULL,
saturation_fraction = 1,
eos = getOption("oceEOS", default = "gsw")
)
salinity |
Either practical salinity (PSU) or a |
pressure |
Seawater pressure (dbar). |
longitude |
Longitude of observation (only used if |
latitude |
Latitude of observation (only used if |
saturation_fraction |
The saturation fraction of dissolved air in seawater,
ignored if |
eos |
The equation of state, either |
If the first argument is an oce object, and if the pressure
argument is NULL, then the pressure is sought within the first
argument. In the case of eos="gsw", then a similar procedure
also applies to the longitude and latitude arguments.
Temperature (degC), defined on the ITS-90 scale.
Dan Kelley
Fofonoff, N. P., and R. C. Millard. “Algorithms for Computation of Fundamental Properties of Seawater.” UNESCO Technical Papers in Marine Research. SCOR working group on Evaluation of CTD data; UNESCO/ICES/SCOR/IAPSO Joint Panel on Oceanographic Tables and Standards, 1983. https://unesdoc.unesco.org/ark:/48223/pf0000059832.
Gill, A E. Atmosphere-Ocean Dynamics. New York, NY, USA: Academic Press,
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, 2010.
McDougall, Trevor J., and Paul M. Barker. Getting Started with TEOS-10 and the Gibbs Seawater (GSW) Oceanographic Toolbox. SCOR/IAPSO WG127, 2011.
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(),
swTSrho(),
swThermalConductivity(),
swTheta(),
swViscosity(),
swZ()
# 1. Test for a check-value given in reference 1. This value, -2.588567 degC,
# is in the 1968 temperature scale (IPTS-68), but swTFreeze reports
# in the newer ITS-90 scale, so we must convert before checking.
Tcheck <- -2.588567 # IPTS-68
T <- swTFreeze(salinity=40, pressure=500, eos="unesco")
expect_equal(Tcheck, T68fromT90(T), tolerance=1e-6)
# 2. Compare unesco and gsw formulations.
data(ctd)
p <- ctd[["pressure"]]
par(mfrow=c(1, 2), mar=c(3, 3, 1, 2), mgp=c(2, 0.7, 0))
plot(swTFreeze(ctd, eos="unesco"),
p, xlab="unesco", ylim=rev(range(p)))
plot(swTFreeze(ctd, eos="unesco") - swTFreeze(ctd, eos="gsw"),
p, xlab="unesco-gsw", ylim=rev(range(p)))