sw.theta {oce}R Documentation

Seawater potential temperature

Description

Compute theta, the potential temperature of seawater.

Usage

  t.potential <- sw.theta(S, t, p, pref=0, 
               method=c("UNESCO1983","Bryden1973"));

Arguments

S in-situ salinity [PSU]
t in-situ temperature [degC]
p in-situ pressure [dbar]
pref reference pressure [dbar]
method algorithm to be used (see details)

Details

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 pref. This quantity is commonly denoted theta(S,t,p,pref) in the oceanographic literature.

The "Bryden1973" method does not use the reference pressure, since it is set up to approximate potential temperature referenced to the surface.

For general use, the "UNESCO1983" method is preferable, since it permits calculation for arbitrary reference pressure. The UNESCO formula is derived from Bryden's earlier method, as Fofonoff et al. (1983) explain.

This is not the place to discuss the two methods in detail, but users may note from the example that the two typically yield values that agree to a few millidegrees.

Value

Potential temperature [degC] of seawater.

Author(s)

Dan Kelley Dan.Kelley@Dal.Ca

References

Bryden, H. L., 1973. New polynomials for thermal expansion, adiabatic temperature gradient and potential temperature of seawater, Deep-Sea Res., 20, 401-408.

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.

See Also

N/A.

Examples

library(oce)
print(sw.theta(35, 13, 1000)) # 12.858

print(sw.theta(40,40,10000,0,"UNESCO1983")) # 36.89073 (Fofonoff et al., 1983)
        
# Demonstrate that the methods agree to a couple of
# millidegrees over a typical span of values
S <- c(30,30,38,38)
T <- c(-2,-2,30,30)
p <- rep(1000,4)                                   
print(max(abs(sw.theta(S,T,p) - sw.theta(S,T,p,0,"UNESCO1983"))))

[Package oce version 0.1.67 Index]