Calculate salinity from what is actually measured by a CTD, i.e.
conductivity, insitu temperature and pressure. Often this is done
by the CTD processing software, but sometimes it is helpful to do this
directly, e.g. when there is a concern about mismatches in sensor
response times. Two variants are provided. First, if eos
is
"unesco"
, then salinity is calculated using
the UNESCO algorithm described by Fofonoff and Millard (1983) as in
reference 1. Second, if eos
is "gsw"
, then the
GibbsSeaWater formulation is used, via gsw::gsw_SP_from_C()
in the gsw package. The latter starts with the same formula
as the former, but if this yields a Practical Salinity less than 2,
then the result is instead calculated using
formulae provided by Hill et al. (1986; reference 2), modified to match the
"unesco"
value at Practical salinity equal to 2 (reference 3).
swSCTp( conductivity, temperature = NULL, pressure = NULL, conductivityUnit, eos = getOption("oceEOS", default = "gsw") )
conductivity  a measure of conductivity (see also 

temperature  insitu temperature (\(^\circ\)C), defined
on the ITS90 scale; see “Temperature units” in the documentation for

pressure  pressure (dbar). 
conductivityUnit  string indicating the unit used for conductivity.
This may be 
eos  equation of state, either 
Practical Salinity.
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.
K. Hill, T. Dauphinee, and D. Woods. “The Extension of the Practical Salinity Scale 1978 to Low Salinities.” IEEE Journal of Oceanic Engineering 11, no. 1 (January 1986): 10912. https://doi.org/10.1109/JOE.1986.1145154.
gsw_from_SP
online documentation, available at
http://www.teos10.org/pubs/gsw/html/gsw_C_from_SP.html
For thermal (as opposed to electrical) conductivity, see
swThermalConductivity()
. For computation of electrical
conductivity from salinity, see swCSTp()
.
Other functions that calculate seawater properties:
T68fromT90()
,
T90fromT48()
,
T90fromT68()
,
swAbsoluteSalinity()
,
swAlphaOverBeta()
,
swAlpha()
,
swBeta()
,
swCSTp()
,
swConservativeTemperature()
,
swDepth()
,
swDynamicHeight()
,
swLapseRate()
,
swN2()
,
swPressure()
,
swRho()
,
swRrho()
,
swSTrho()
,
swSigma0()
,
swSigma1()
,
swSigma2()
,
swSigma3()
,
swSigma4()
,
swSigmaTheta()
,
swSigmaT()
,
swSigma()
,
swSoundAbsorption()
,
swSoundSpeed()
,
swSpecificHeat()
,
swSpice()
,
swTFreeze()
,
swTSrho()
,
swThermalConductivity()
,
swTheta()
,
swViscosity()
,
swZ()
# 1. Demonstrate agreement with test value in UNESCO documents swSCTp(1, T90fromT68(15), 0, eos="unesco") # expect 35#> [1] 35# 2. Demonstrate agreement of gsw and unesco, S>2 case swSCTp(1, T90fromT68(15), 0, eos="gsw") # again, expect 35#> [1] 35# 3. Demonstrate close values even in very brackish water swSCTp(0.02, 10, 100, eos="gsw") # 0.6013981#> [1] 0.6013981swSCTp(0.02, 10, 100, eos="unesco") # 0.6011721#> [1] 0.6011721