Add trarho field

Author: amorison

stagpy/phyvars.py

@@ -20,6 +20,7 @@
     ('eta', Varf('Viscosity', 'Pa.s')),
     ('rho', Varf('Density', 'kg/m3')),
     ('rho4rhs', Varf('Density term in RHS', 'kg/m3')),
+    ('trarho', Varf('Density from tracer mass', 'kg/m3')),
     ('sII', Varf('Second invariant of stress tensor', 'Pa')),
     ('sx1', Varf('1st comp. of principal stress eigenvector', 'Pa')),
     ('sx2', Varf('2nd comp. of principal stress eigenvector', 'Pa')),
@@ -72,6 +73,7 @@
     ('Viscosity', ['eta']),
     ('Density', ['rho']),
     ('Density4rhs', ['rho4rhs']),
+    ('TraBasedDensity', ['trarho']),
     ('water', ['wtr']),
     ('Age', ['age']),
     ('ContinentNumber', ['contID']),