RELEASE NOTES for CAMx v7.20, 04/30/22 The Comprehensive Air Quality Model with extensions (CAMx) is available at www.camx.com. Overview of Version 7.20 ------------------------ V7.20 includes new features, modifications, and bug fixes from the previous release (v7.10) * Use the chemistry parameters files specifically labeled for v7.2. * Use the TUV photolysis pre-processor specific to v7.2. * Check the CAMx control namelist template for the full list of control variables specific to this version. * The operation of the CAMx makefile has not changed since the last version. Type "make" or "make help" for more information. NOTE: RECENT VERSIONS OF THE GFORTRAN COMPILER WILL NOT COMPILE CAMx WITH OMP PARALLELIZATION BECAUSE OF AN INCOMPATIBILITY WITH BLOCK DATA IN ISORROPIA. THIS IS NOT AN ISSUE WITH OTHER SUPPORTED COMPILERS. OPTIONS: a) USE MPI ONLY WITH GFORTRAN b) REVERT BACK TO AN OLDER VERSION OF GFORTRAN c) USE A DIFFERENT COMPILER v7.20 New Features and Major Updates ------------------------------------ 1. Announcing the Cloud-in-Grid (CiG) convective mixing model. Implications: This feature was implemented in 2015 but not advertised. CiG comprises an entraining/detraining plume model that treats shallow to deep vertical mixing within sub-grid convective clouds. This option requires specific meteorological input variables from the WRF multi-scale Kain-Fritsch (MSKF) cumulus model. CiG can result in significant modifications to vertical pollutant concentration profiles for grid columns containing convective activity. CiG does not yet operate with any of the Probing Tools. See the CAMx User's Guide for a full description. 2. A Stratospheric Ozone Profile Scheme has been added for hemispheric applications. Implications: This is a simple scheme that defines stratospheric ozone profiles based on independently derived inputs of time- and space-varying top boundary conditions. The purpose of this module is to maintain stratospheric ozone profiles above the tropopause during long simulations without the need to include an explicit stratospheric chemistry mechanism. We recommend against using the scheme for urban to continental scale applications. OSAT has been updated to accommodate the stratospheric ozone module, but no other Probing Tools are yet supported. 3. A new PPM solver option has been added for vertical advection. Implications: The PPM scheme is an alternative to the original CAMx implicit backward-Euler hybrid integration scheme. While both are designed to limit numerical diffusion, PPM is less numerically diffusive but as an explicit scheme it requires multiple sub- steps to ensure a stable solution, whereas the original implicit scheme is more diffusive but may run somewhat faster. PPM operates with all Probing Tools. v7.20 Modifications ------------------- 1. Removed the Carbon Bond version 2005 (CB05) photochemical mechanism. Implications: CB05 is now obsolete and has since been superseded by five releases of CB6 over the past 10 years. The next major update to Carbon Bond will be CB7 expected in the next release. 2. Added new option to output gas concentrations in units of ug/m3, rather than the default ppm units. Implications: This option helps certain users who need to compare gas concentration predictions to measurement data in ug/m3. 3. Added the ability to bypass Ix in-line and gridded input emissions for CB6. Implications: CB6 has included marine iodine chemistry since CB6r4, where oceanic Ix emissions are estimated either in-line as CAMx runs or from input gridded emissions, otherwise the model stops with an error. This created a burden for CAMx applications that do not include oceans in the domain. The "Inline_Ix_Emissions" flag has been updated from a T/F logical to a character flag that allows for "TRUE" (use in-line Ix emissions), "FALSE" (use input gridded emissions), or "BYPASS" (ignore all Ix emissions). The BYPASS option still runs Ix chemistry in CB6, but the model allows for zero Ix emissions. 4. Updated the global average CH4 concentration used for chemistry from 1.75 to 1.85 ppm Implications: This update reflects current global CH4 levels, which is used in the photochemical mechanisms. The model continues to allow for a separately emitted CH4 (ECH4) species provided by emission files. Expect very small effects on ozone concentrations. 5. Updated surface UV albedo for 2 landuse classifications based on more recent published data. Implications: Albedo for water and barren land were increased by a few percentage points to 7% and 10%, respectively. Expect small effects on ozone concentrations. 6. Updated SAT to read netCDF initial/boundary condition input files. Also fixed a bug in reading/counting SAT tracer variables on initial/boundary condition files. Implications: In prior versions, the SAT initial/boundary condition input files needed to be in Fortran binary format. Initial/boundary condition pre-processors have been updated to generate netCDF formats. 7. Numerous minor updates in RTRAC/RTCMC to increase flexibility in defining tracer chemistry. Implications: Updates include: a) Factors can be applied to RTCMC photolysis rates that point to core mechanism reaction rates. b) RTRAC reads reaction rates in molecular units instead of ppm units, as the former is more commonly reported. c) Improved the method to define octanol partitioning coefficient (Koa) for semi-volatile organic tracers that may exist as a gas or aerosol. 8. Updated RTRAC/RTCMC to output deposition files like the core model and SAT. Implications: RTRAC calculates deposition of gas and PM tracers, but up to now did not write deposited mass to gridded output files. However, RTRAC had written surface model mass burdens to output files if the RTRAC surface model was invoked. Now, depending on the RTRAC surface model flag, either tracer deposition (F) or surface model tracer masses (T) are written to output files. 9. Added additional diagnostics and error messages: 1) Error/stop when SAT/APCA = "TRUE" and less than 2 source groups are specified (biogenics must be specified as group #1, and at least one other group must be specified). 2) Error/stop when no gridded emission are provided but the gridded emissions flag is "TRUE" 3) Removed check on point source region override flag when only 1 SAT region is specified. Implications: These additional checks help the user understand issues with the CAMx run configuration and keeps the model from crashing or generating spurious results. v7.20 Bug Fixes --------------- 1. Updated the definition of VAR (dimension), NVARS (global attribute) and VAR-LIST (global attribute) in all netCDF I/O files for consistency. Several other minor netCDF bug fixes, mostly related to global attributes. Added NCF error codes to CAMx error messages related to NCF problems. Implications: Now VAR and NVARS consistently define the number of time- varying variables in all files, which are listed in the VAR-LIST global attribute. 2. Fix Probing Tool bug that prevented writing of restart files when only 1 grid is active. Implications: This bug affected the generation of restart files for several Probing Tools. 3. Fix bug in initializing count of emissions files (RTRAC/startrt.f) Implications: RTRAC continues to require a single gridded and point emission files, and so this count was not used. This alleviates a runtime error on initialization. RTRAC emission file variables in the CAMx control namelist file are not indexed by emission sector. 4. Fix bug initializing point source data structures when point sources were not supplied. Implications: When running without point source inputs with SAT invoked, datasets were accessed that were not initialized, causing a runtime error. 5. Fix bug writing topographic fields to Probing Tool output files. Implications: Previously topographic fields were defined but not written. 6. Fix minor mathematical error in the UTM<->geodetic conversion subroutine. Implications: The math error is reported to have resulted in up to 7 meter differences in UTM coordinates. 7. Fix the calculation of wet deposition liquid water concentration output fields. Implication: Values of liquid concentration written to gridded deposition files were too low because of two numerical errors related to time-averaging rather than time-accumulating. 8. Revised the naming convention for output deposition variables. Implications: This was done to maximize species string length and to be consistent with deposition variable names generated by the Probing Tools. Now the naming is: R_species (dry deposition velocity) D_species (dry deposition) W_species (wet deposition) L_species (liquid concentration) 10. Fixed bug looking for incorrect NCF file type for initial concentration in DDM input files. Implications: This bug led to CAMx initialization failure when checking the file type. 11. Fix bug in SAT timestamp when crossing over the new year. Implications: Alleviates run-time error in crossing new year. 12. Fix various bugs in reading NCF DDM/RTRAC point source file headers. Implications: Alleviates startup crashes when reading these files. 13. Ensure true latitudes for Lambert projection parameters are written to model output files in the correct order. Implications: Incorrect order caused certain Models3/IOAPI post-processing programs to fail. 14. Fixed bug that was prohibiting VBS emission species from being injected into the grid system. Implications: This bug was introduced in v7.0 with the expansion to use multiple input emission files. VBS will now generate OA concentrations.