open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi There,

I may be asking a stupid question but I am a little confused about the units of the salinity tracer within TELEMAC-3D

The manual states that these units should be specified in g/L, however this is obviously dependent on the density of the water which in the case of saline water is higher. More commonly units of ppt, PSU, g/kg are used for measurement of salinity concentrations which are not dependent on the density.

From my understanding the specified units do not actually have an affect on the concentration gradients and resulting advection-diffusion, however they do have an affect on the Law of State used to estimated the density of the fluid.

The manual states that the 'First Law' uses units of g/L to estimate the density. I see people on the forums using ppt and PSU as input values for salinity concentration but is this entirely correct considering the calculation of the density considers g/L?

Can somebody shed some light on exactly what is going on here please?

Regards,
Toby

After i doing a bit more searching I managed to find that the formulation used by telemac for the estimation of density and salinity is from Lang (1990) and is specified in units of PSU. Please see attached exert of reference from the following book "Resource Recovery, Confinement, and Remediation of Environmental Hazards".

In this is the case then using PSU as input in telemac should equate to the correct formulation of the fluid density based on Density Law 3.

Can anybody confirm?

Hello,

The reference is actually given in my book, it is the equations of state established by UNESCO in: International Oceanographic Tables, Volume 4. UNESCO Technical papers in marine science, n°40. 1987.

Salinity is indeed in kg/m3, and salinity according to Unesco is based on the electric conductivity of water compared to that of a solution of potassium chloride. The salinity in kg/m3 deduced from conductivity is thus in theory only valid for this salt.

With best regards,

Jean-Michel Hervouet