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Logical switch(s) (T/F) used to activate tracers point Sources/Sinks (like river runoff) and to specify which tracer variables to consider. Only NAT active tracers (temperature, salinity) and NPT inert tracers need to be specified here.
dimension = LtracerSrc(MT,Ngrids)
routine = mod_scalars.F
keyword = LtracerSrc
input =,,,,,,
Other biological and sediment tracers switches are activated in their respective input scripts.
In nesting applications, turn on only the grids that require activation and processing of tracers point Sources/Sinks.

Recall that switches are usually activated to add river runoff as a point source. At minimum, it is necessary to specify both temperature and salinity for all rivers. The other tracers are optional.

This logical switch replaces and eliminates the need to have or read the variable river_flag(river) from the input rivers forcing NetCDF file:
double river_flag(river)
river_flag:long_name = "river runoff tracer flag"
river_flag:option_0 = "all tracers are off"
river_flag:option_1 = "only temperature"
river_flag:option_2 = "only salinity"
river_flag:option_3 = "both temperature and salinity"
river_flag:units = "nondimensional"

The above variable was too cumbersome and complicated when additional tracers are considered. However, this change is backward compatible.

The LtracerSrc switch will be used to activate the reading of respective tracer variables from the input river forcing NetCDF file (SSFNAME). If you want to add other tracer variables (other than temperature and salinity) as a source for a particular river(s), you just need to specify such values on those river(s). Then, set the values to ZERO on the other river(s) that do NOT require such river forcing for that tracer. Remember that you need to specify the tracer values for all rivers, even if their values are zero.