Salinity is the saltiness or dissolved salt content of a body of water. Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it [wiki]. Salinity cannot not be measured directly, but needs to be calculated from conductivity measurements. Salinity is most commonly reported using the Practical Salinity Scale 1978, a scale developed relative to a standard potassium-chloride solution and based on conductivity, temperature and barometric pressure measurements. Salinity expressed in the PSS is a dimensionless value, although by convention, it is reported as practical salinity units (psu). Salinity in practical salinity units is nearly equivalent to salinity in parts per thousand [usgs].
Diver-Office (version 2016 and higher) offers the option to export salinity data to Excel. Figure 1 shows the Default Export Settings with the salinity export data option highlighted. The salinity data can only be exported for CTD-Divers. Salinity data cannot be shown in Diver-Office.
Figure 1 - File export settings as used in Diver-Office 2016.
Computation of Salinity
If specific conductivity values have been compensated to 25 °C and water depths are sufficiently shallow that pressure corrections are not necessary, salinity can be calculated using the conductivity measured by the CTD-Diver. The salinity is expressed in practical salinity units (psu). The relationship between specific conductivity and salinity is shown in Figure 2. The underlying data set is listed in Table 1 and obtained from [usgs].
In case the CTD-Diver is set to measure conductivity instead of specific conductivity at 25 °C the conductivity will be converted
Where Cs is the specific conductivity at 25 °Cm and Tm are the measured conductivity and temperature, respectively.
Figure 2 - Conversion of specific conductivity, in millisiemens per centimeter, to salinity, in practical salinity units [wiki].
Table 1 - Rating table for conversion of specific conductivity, in millisiemens per centimeter, to salinity, in practical salinity units [usgs].