new feature - tracer

[nmizukami]

Goal: to enable to trace DOC/DON (or other constituents) from land models

Urgency: months to a year

Background: Use advection-dispersion equation dC/dt = -UdC/dx + Dd2C/dx2 where C = concentration [M/L3], U = velocity [L/T], D=dispersion coefficient [L2/T] 1st term in LHS = advection 2nd term in LHS = dispersion

Tasks:

• [ ] Receive/process DOC/DNC variables from NUOPC coupler

• [ ] add subroutine to solve mass balance equation per reach start with advection only equation.

Relevant issues:

153

ESCOMP/CTSM#1216

[ekluzek]

Note another desired use of this capability is for water isotope tracers needed for example in Paleo work.