Mercury

Hello Team-Hg

Here's the list of things I *think* we came up with on Friday regarding cleaning up the code (feel free to add/comment):

1) Standardize the solver. Everyone should use the solver Chris developed for the Hg chemistry
(located at ~cdh/GC/RevisedChem.v7-04-06/mercury_mod.f)

• outstanding issue - dry dep of Hg0* <- currently working on this (eds)

2) Catalog all emissions options and develop clear flagging system to choose your own adventure. This will include:

• different anthropogenic emissions scenarios/corrections (i.e Jaffe vs. Streets) <- going to work on the anthro emissions soon (eds),
  
• different land emissions. <- nvd will work on this

3) Diagnostics. See separate section below.
4) Comment everything in the code. Remove old bits of code that are hanging around & commented out.
5) GEOS-5
6) Get the land stuff out of ocean_mercury_mod.f and into it's own module <- nvd will work on this

Chemistry 'issues'

1) Oxidant. Chris has a simulation with Hg-Br chemistry and SS aerosol deposition; the global budget is ok, but the Br concentrations in the BL are too low to generate diurnal cycles. (cdh working on it)
2) Snow/ice scavenging of HgII
3) Dry deposition of "aqueous HgII. (Explanation from Chris: We calculate the fraction of HgII, Fg, which is gas phase. But we're currently applying the dry deposition velocity to both gas and aqueous fractions. I think it would be better to deposit the aqueous fraction at the velocity of HgP; this would be slower dep, but I don't know how much. This is definitely up for discussion.)

Diagnostics

Here's the list of current Hg diagnostics (ND03) http://www-as.harvard.edu/chemistry/trop/geos/doc/man/appendix_5.html Here are some suggested changes:

1. The ocean Hg0, Hg2, HgC should have concentration units not kg. Is 'molar' the best choice? Fluxes of these should be in concentration/time, not kg/s.
2. The ocean restart files should have concentration units not kg. They currently use the category 'OCEAN-HG' which would make sense for the ND03 ocean Hg0, Hg2, HgC output too.
3. 'PL-HG2-$' doesn't really describe all of the fluxes in our model. There are a lot of diagnostic quantities which are either chemical P/L fluxes or rate constants. I think these should all be in one diagnostic called something like 'PL-HG-$' (or maybe 'PL-HG-A', 'PL-HG-O' to separate the atmosphere and ocean). The fluxes in this diagnostic would include redox in air and water, colloidal sinking, ocean-atmosphere piston velocity, ...