RELEASE_NOTES for CMAQv4.7.1 - 16 June 2010


The changes and new features of this release are:

1) Aqueous chemistry

      - Mass conservation improvements
        + Imposed 1 second minimum timestep for remainder of the cloud lifetime
      	  after 100 "iterations" in the solver
        + Force mass balance for the last timestep in the cloud by limiting
          oxidized amount to mass available
      - Implemented steady state assumption for OH
      - Only allow sulfur oxidation to control the aqueous chemistry solver
        timestep (previously, reactions of OH, GLY, MGLY, and Hg for
        multipollutant model also controlled the timestep)

2) Advection

      - Added additional divergence-based constraint on advection timestep
      - Vertical advection in the Yamo module is now represented with 
        the PPM scheme to limit numerical diffusion

3) Model time step determination

      - Fixed a potential advection time step error reported by Talat Odman
        + The sum of the advection steps for a given layer time step might
          not equal the output time step duration in some extreme cases
        + Ensured that the advection steps sum up to the synchronization step

4) Horizontal diffusion

      - Fixed a potential error reported by Talat Odman
        + Concentration data may not be correctly initialized if multiple
          sub-cycle time steps are required
        + Fix to initialize  concentrations with values calculated in the
          previous sub-time step

5) Emissions

      - Bug fix in EMIS_DEFN.F to include point source layer 1 NH3 emissions
      - Bug fix to calculate soil NO "pulse" emissions in BEIS
      - Remove excessive logging of cases where ambient air temperature exceeds
        315.0 Kelvin. When this occurs, the values are just slightly over 315
      - Bug fix for parallel decomposition errors in plume rise emissions

6) Multipollutant model updates

      - Bug fix to facilitate in-line emissions option
      - Mercury
        + Dicarboxylic acid reduction mechanism applied to aqueous phase
          oxidized mercury species
        + Cl oxidation pathway based on Donohoue et al 2005 J. Phys. Chem.
          A 109(34)
      - Lowered CB05 mechanism unit yields for acrolein from 1,3-Butadiene
        tracer reactions to be consistent with laboratory measurements

7) Fixed possible parallel processing problem

      - Processor 0 creates the NetCDF, I/O-API file header when opening new
        output files, and all writes to the file are accomplished through
        processor 0 via the pario library.
        + Since the program pointer will not be at the same part of the code
          in each parallel processor, Message Passing Interface (MPI) barriers
          have been used to synchronize file access with other processors.
        + However, hardware latency may affect this MPI synchronization, in
          that all program pointers have reached the barrier, which is then
          passed, and a non-0 processor will try to access a file before the
          hardware has actually created it resulting in a "hung" execution or
          a crash.
        + In all cases, non-0 processors don't need imminent access to these
          files, and the problem is fixed by removing the barriers and the
          immediate subsequent file access, since the necessary access for
          these processor's occurs later in the computation.

8) Photolysis

      - JPROC/phot_table and phot_sat options
        + Expanded lookup tables to facilitate applications across the globe and
          vertical extent to 20km
        + Updated temperature adjustments for absorption cross sections and
          quantum yields
        + Revised algorithm that processes TOMS datasets for OMI data format
      - In-line option
        + Asymmetry factor calculation updated using values from Mie theory
          integrated over log normal particle distribution; added special
          treatment for large particles in asymmetry factor algorithm to avoid
          numerical instabilities

9) Instrumented Models

      - DDM-3D
      - Sulfur Tracking
      - Primary Carbon Apportionment