The extension of the Practical Salinity Scale 1978 to low salinities

The Practical Salinity Scale (PSS) 1978 is defined only for salinities within the range 2-42. We have investigated the relationship between mass-determined salinity, electrical conductivity, and temperature for salinities between 0 and 2 with the aim of developing an extension to the Practical Salinity Scale 1978. The paper presents our data, on the basis of which the following correction is proposed to extend the validity of the equations defining the scale to the entire 0-42 range:
S=\sum\min{i=0}\max{5} (a_{i}+b_{i}f(t))R_{t}^{i/2}-\frac{a_{0}}{1 + 1.5x + x^{2}}-\frac{b_{0}f(t)}{1+y^{1/2} + y + y^{3/2}}
where
f(t)=\frac{(t-15)}{1 + k(t-15)
x=400R_{t}
y=100R_{t}
and the constant
a_{i}, b_{i}
, and
k
are defind by the Practical Salinity Scale 1978.