CMAQv5.0.2 Hg bidirectional exchange
The Mercury (Hg) bidirectional exchange algorithms could crash under conditions when the solution to surface concentrations and fluxes became stiff. This typically happened when one of the concentrations in the surface media and/or the atmosphere in the system of equations was orders of magnitude larger than the others. This was addressed through better error trapping and making more variables and functions double precision to better handle the numerical precision needed to solve the system of equations under these conditions.
Significance and Impact
No significant impact on the run time or model Hg concentration fields or deposition.
Jesse Bash, Atmospheric Modeling and Analysis Division, U.S. EPA