RELEASE NOTES for CAMx v6.00, 05/06/13 The Comprehensive Air Quality Model with extensions (CAMx) is available at http://www.camx.com. Overview of Version 6.00 ------------------------ V6.00 is a major update from the previous release (v5.41). The biggest changes affecting established users is the updated Fortran binary I/O file formats and the revised approach for generating photolysis inputs. New features and capabilities, modifications, and bug fixes are listed below. * Use the chemistry parameters files specifically labeled for v6.00. * Formats and contents for meteorological, landuse, albedo/haze/ozone, and photolysis rates files have changed signficantly, as described below. * The CAMx namelist control file has changed significantly in this release; refer to the namelist template provided with the source code and the User's Guide for a full list of namelist variables. Guidance for running MPI and OMP parallelization is provided in the README file located in the source code directory, and in the CAMx User's Guide. v6.00 Major Updates and New Capabilities ---------------------------------------- 1. Revised Fortran binary I/O file format. All major gridded input/output fields are now in a common format; this includes all input meteorology, landuse, IC/BCs, emissions, and output concentration/deposition fields. While overall the format is consistent with the original CAMx/UAM output format, the file headers have been updated to include additional information on map projection, grid specifications, time zone, and various field-specific flags. See the User's Guide for more information. Implications: The biggest change is to meteorological and landuse file formats. These are now provided in 5 files: 2-D time- invariant, 2-D time-variant, 3-D time-variant, 3-D Kv, and 3-D cloud/rain. Landuse must now be developed for 26 Zhang LU categories, CAMx internally maps these to 11 LU categories if Wesely deposition is invoked. Only the headers of IC/BC, emissions and output concentration/deposition files have been changed. PRE-EXISTING IC/BC AND EMISSION FILES CAN BE USED WITH V6.00 FOR BACKWARD COMPATIBILITY, BUT METEOROLOGICAL INPUT FILES MUST BE GENERATED SPECIFICALLY FOR V6.00. Several pre-processors are available that generate the new input file formats. Some post-processing programs are also udpated to use the new information on the output file headers. Programs that read output concentration/deposition files can read both the old and new file formats but they will ignore the new header information (e.g., PAVE, VERDI, CAMxPOST, CAMxTRCT, etc.). 2. Revised the process to generate photolysis (J) rates and their use in CAMx. Implications: (1) The albedo/haze/ozone file now contains only ozone column data: a) Albedo is internally set within CAMx from input LU and snow cover; b) Haze is internally set within CAMx from the PM simulation, or a default haze profile is set for non-PM runs. c) Optional snow-cover is moved to the 2-D met file; d) Optional drought and surface roughness are removed; e) Optional land/ocean mask is still allowed. CAMx namelist variable "Albedo_Haze_Ozone" is now "Ozone_Column". USE THE NEW "O3MAP" PRE-PROCESSOR TO GENERATE THIS FILE. (2) TUV generates a clear-sky J lookup table for the following dimensions: O3 column (input), altitude above ground (input), terrain height (default), albedo (default), solar zenith (default). A single default haze profile is used in TUV. USE THE LATEST VERSION OF TUV TO GENERATE THIS FILE. (3) CAMx interpolates lookup J rates to cell-specific values of solar zenith, height above ground, terrain height, and albedo; then photolysis rates are adjusted for clouds and haze using the in-line TUV; then certain photolysis rates are adjusted for temperature and pressure. (4) The RADM cloud adjustment has been removed. TUV is now the only cloud/haze adjustment scheme. CAMx namelist variables "TUV_Cloud_Adjust" and "TUV_Aero_Adjust" have been removed. 3. Mercury chemistry has been updated to include adsorption of Hg(II) to PM and gas-phase reactions with ambient bromine. Gas-phase reactions with ambient molecular chlorine (Cl2) have been removed. The dry deposition velocity for Hg(0) is set to zero for ocean cells. Implications: 2 new Hg species: HGIIP for gas phase HG(II) adsorbed onto fine PM; HGIIPC for gas phase HG(II) absorbed onto coarse PM. Differences in Hg(0) and Hg(II) concentrations/deposition may be significant. 4. Removed the vertical nesting capability in CAMx. Implications: This rarely used feature was removed as it does not contribute significantly to runtime efficiency, leads to numerical problems along nested grid boundaries, and complicates code structures in several areas. NOTE: Namelist variable "Number_of_Layers" has been changed from an array to a scalar. v6.00 Modifications ------------------- 1. Added a new namelist "Flexi_Nest" flag to explicitly allow flexi-nesting of meteorological, emissions, and initial condition inputs. Implications: This change should help control cases in which input files are erroneously left out of a simulation when the user meant to include these files. If the flag is FALSE, CAMx will require all gridded fields to be provided for all grids and will stop with an error message if any are missing. If the flag is TRUE, CAMx will interpolate any missing fields from their parent grids, as has been traditionally allowed for flexi-nesting cases. 2. Removed the namelist variable defining number of time-averaged output species "Number_of_Output_Species". Implications: Now this number is internally calculated from the list of user- defined species according to the namelist variable array "Output_Species_Names()". 3. The chemistry parameters file now provides molecular weights for all gas species explicitly, rather than a "diffusivity ratio" parameter. A few other deposition parameters for gas species have been updated. Implications: The diffusivity ratio is now calculated internally from the molecular weight. This should be a mostly transparent change from the users standpoint, while providing a source of molecular weight information for the user's reference. 4. Revised the implementation approach for the plume distribution override feature added to v5.41. Implications: Plume distribution override is now invoked by setting the hourly stack flow rate value to a negative value (representing plume bottom in meters) and the plume height override to a negative value (representing plume top in meters). Negative stack height is no longer used for plume bottom as it is not a time-varying variable on the point source file. Plume bottom and top can be the same value, and all plume mass will be injected into the single layer at that altitude. Plume distribution override cannot be used with PiG. 5. Improved the cloud adjustmnet to solar flux calculation in dry deposition. Implications: Prior adjustment relied on cloud fraction, which is either 1 or 0 in CAMx. Now the adjustment is based on cloud optical depth, consistent with the cloud adjustment on photolysis rates. Minor impacts to deposition velocity should be expected. 6. Lowered minimum threshold windspeed to 0.1 m/s in MICROMET.F. Implications: This change is to ensure consistent calculations of stability variables at low windspeed whenever MICROMET is called. Negligible impacts are expected. 7. Removed CPU timing calls reported to the CAMx .out file Implications: MPI applications resulted in garbage values reported for CPU times for each process. Now CAMx simply reports "Done" after each process has successfully completed. 8. Improved technique for solution convergence in RADM-AQ aqueous PM chemistry routine. Implications: In rare instances, RADM-AQ would not converge to a solution in cases with low cloud water content and extremely low pH, stopping the model with an error. This change improves the convergence technique toward a solution. 9. In-line TUV cloud/aerosol photolysis rate adjustment is now called at each individual timestep in each grid, instead of once per meteorological update (usually 1 hour). Implications: This change addresses an MPI incompatibility. This should improve TUV response to evolving PM field each timestep, minor impacts to ozone and secondary PM concentration should be expected. v6.00 Bug Fixes --------------- 1. Fixed a bug that was not properly initializing CPA variables for OH and HO2 termination rates in Mechanism 5 (SAPRC99). Fixed an incorrect assignment for the O3-O1D photolysis reaction rate. Implications: These minor fixes will lead to correct rates for these specific variables in the CPA output files. No impact to the core model results. 2. Fixed a bug in OSAT/APCA and PSAT that can incorrectly assign point sources to source regions under very specific conditions. Implications: This bug may cause incorrect source attribution for point sources under the following conditions: 1) 3 or more grids in a telescoping configuration; 2) leftover group is turned on; 3) the leftover group includes point sources. The bug only occurs in the 3rd or deeper grid, not the master or 2nd grids. The calculation for actually injecting the emissions is correct, just the assignment to source region is possibly in error. 3. Iodine radicals have been correctly ordered in the chemistry parameters files for iodine mechanisms to support running the IEH solver. Implications: The IEH solver requires a very specific order for radicals. This change has no impact running iodine mechanisms with EBI or LSODE solvers. 4. Removed the condition that PM must be run in order to calculate a heterogeneous N2O5 hydrolysis rate. Implications: An update in v5.41 to set a minimum heterogeneous N2O5 hydrolysis rate in ozone-only runs (no PM) was added to the KHETERO subroutine (see v5.41 Release Notes, Modification 3). But a conditional restricting KHETERO to be called only during PM runs was not removed, thus negating the v5.41 update for ozone-only runs. This change removes the PM requirement, so KHETERO is now always called. 5. Fixed a bug in PiG when running MPI that could lead to incorrect information about which MPI domain slice a PiG puff resides. Implications: When running PiG with MPI, domain slice location information was not updated among all processors when some puffs traversed domain slice boundaries during transport, leading to improper slice locations for one timestep. Slice information is now properly updated among all processors each timestep. Scattered and sporadic concentration differences related to PiG dumping (usually minor) are to be expected for MPI runs, but PiG differences between MPI and non-MPI runs should be alleviated.