E-mail from Shawn Roselle to OAQPS Air Quality Modeling Group on
4/09/2007 explaining the differences between the v4.6 release version of
CMAQ and the internal version (v4.6.1).  The internal version was used
for the Ozone NAAQS Final Rule RIA.

---

An internal version of CMAQ (v4.6.1i) is being made available for
testing/use.  The version includes options for the CB05 chlorine
chemistry and the multipollutant model, as well as updates to the
mercury, toxics, and base model options.  The changes and new features
of this internal version are:

1) Multipollutant Model

      - Added multipollutant model option

2) Chlorine Chemistry

      - added option for CB05 with chlorine chemistry for the base model

3) Air Toxics

      - Bug fixes: corrected emissions surrogates for OXYL and PXYL
species

        indices; corrected minimum length for species name (LEN_NAME);

        corrected the max number of bimolecular reactions (N_BI_LOSS);

        initialized variables for mode merging in routine AEROPROC (PHM3

        and FM3); corrected initialization of mode pairs and number of

        trace species

      - revisions:  renamed chlorine emissions surrogate to CL2; turned

        on emissions of CL2 and HCL; removed HOCL from emissions
surrogate

        list; renamed emission surrogates to correspond with new
emissions

        inventory

4) Mercury

      - turned on HCL emissions; removed HOCL from the emissions
surrogate

        list

      - reduced minimum Cl- concentration in cloudwater to 1e-10 (mol/L)

5) Clouds

      - removed aerosol data transformations using Avogadros number
which 

        may cause denormalized numbers

      - in routine getalpha, added parentheses to force the order of

        evaluation (to avoid overflows)

      - in routine aqchem, limit integration timestep by cloud washout
time

6) Vertical Diffusion

      - in ACM2, initialize MBARKS and MDWN to zero for all layers

      - for aerosol emissions, added capability for emission files that

        contain POC or POA

      - for deposition velocity calculations, added logic to avoid
divide

        by zero in calculating the fraction of SOA in j-mode

The source codes for various versions of the model are located on amber.
 The base directory is /amber/home/sjr/share/oaqps, with each model
version located in subdirectories as follows:

BLD_L3b  -- CMAQv4.6.1i, Base model (without chlorine chemistry), cb05,
aero4

BLD_L3c  -- CMAQv4.6.1i, Chlorine model, cb05cl, aero4

BLD_L3h  -- CMAQv4.6.1i, Mercury model, cb05hg, aero4

BLD_L3t  -- CMAQv4.6.1i, Toxics model, cb05cltx, aero4

BLD_L3th -- CMAQv4.6.1i, Multipollutant model, cb05txhg, aero4

I've included the build scripts for each model so that you can see
exactly which model options (modules and include files) were used to
create the source code directories.  The build script are named
bldit.cctm.L3b, bldit.cctm.L3c, etc.

Let me know if you have any questions.

Shawn J. Roselle

NOAA Atmospheric Sciences Modeling Division

In partnership with the U.S. Environmental Protection Agency

Mail Drop E243-03

109 T.W. Alexander Drive

Research Triangle Park, NC 27711

Phone:  919-541-7699

Email:  roselle.shawn@epa.gov

