TOMAS aerosol microphysics
Overview
The TwO-Moment Aerosol Sectional (TOMAS) microphysics package was developed for implementation into GEOS-Chem at Carnegie-Mellon University. Using a moving sectional and moment-based approach, TOMAS tracks two independent moments (number and mass) of the aerosol size distribution for 30 size bins. It also contains codes to simulate nucleation, condensation, and coagulation processes. The aerosol species that are considered with 30-bin size resolution are sulfate, sea-salt, BC/OC, EC, and dust.
Authors and collaborators:
- Peter Adams (Carnegie-Mellon U.) -- Principal Investigator
- Win Trivitayanurak (Carnegie-Mellon U. -- now at U. Edinburgh)
- Dan Westervelt (Carnegie-Mellon U.)
- Jeffrey Pierce (Dalhousie U.)
Questions regarding TOMAS can be directed at Dan (e-mail linked above).
--Dan W. 11:53, 27 January 2010 (EST)
Tracers
TOMAS is a simulation type 3 and utilizes 310 tracers. Each aerosol species requires 30 tracers for the 30 bin size resolution. Here is the (abbreviated) default setup in input.geos (see run.Tomas directory):
Tracer # Description MW (g/mol) 40 H2SO4 98.0 41-70 Number 1.0 71-100 Sulfate 96.0 101-130 Sea-salt 58.5 131-160 Hydrophilic EC 12.0 161-190 Hydrophobic EC 12.0 191-210 Hydrophilic OC 12.0 211-240 Hydrophobic OC 12.0 241-271 Mineral dust 100.0 271-310 Aerosol water 18.0
--Dan W. 21:08, 28 January 2010 (EST)
Implementation notes
As of Jan 27, 2010, TOMAS is currently being implemented into GEOS-Chem v8-02-05 (version in testing).
Code structure
The main-level Code directory has now been divided into several subdirectories:
GeosCore/ GEOS-Chem "core" routines GeosTomas/ Parallel copies of GEOS-Chem routines that reference TOMAS GeosUtil/ "Utility" modules (e.g. error_mod.f, file_mod.f, time_mod.f, etc. Headers/ Header files (define.h, CMN_SIZE, CMN_DIAG, etc.) KPP/ KPP solver directory structure bin/ Directory where executables are placed doc/ Directory where documentation is created help/ Directory for GEOS-Chem Help Screen lib/ Directory where library files are placed mod/ Directory where module files are placed obsolete/ Directory where obsolete versions of code are archived
Because there were a lot of TOMAS-related modifications in several GEOS-Chem "core" routines, the routines that need to "talk" to TOMAS were placed into a separate subdirectory named GeosTomas/. The files in GeosTomas are:
Files: ------ Makefile -- GEOS-Chem routines that have been aero_drydep.f modified to reference the TOMAS aerosol carbon_mod.f microphysics package. These are kept chemdr.f in a separate GeosTomas directory so that chemistry_mod.f they do not interfere with the routines cleanup.f in the GeosCore directory. diag3.f diag_mod.f The GeosTomas directory only needs to diag_pl_mod.f contain the files that have been modified drydep_mod.f for TOMAS. The Makefile will look for dust_mod.f all other files from the GeosCore directory emissions_mod.f using the VPATH option in GNU Make. gamap_mod.f initialize.f NOTE to GEOS-Chem developers: When you input_mod.f make changes to any of these routines isoropia_mod.f in the GeosCore directory, you must also logical_mod.f make the same modifications to the ndxx_setup.f corresponding routines in the GeosTomas planeflight_mod.f directory. seasalt_mod.f sulfate_mod.f Maybe in the near future we can work tomas_mod.f towards integrating TOMAS into the GeosCore tomas_tpcore_mod.f90 directory more cleanly. However, due to tpcore_mod.f the large number of modifications that were tpcore_window_mod.f necessary for TOMAS, it was quicker to tracerid_mod.f implement the TOMAS code in a separate wetscav_mod.f subdirectory. xtra_read_mod.f -- Bob Y. (1/25/10)
Each of these files were merged with the corresponding files in the GeosCore subdirectory. Therefore, in addition to having the GEOS-Chem modifications from v8-02-05, these files also have the relevant TOMAS references.
A few technical considerations dictated the placing of these files into a separate GeosTomas/ directory:
- The ND60 diagnostic in the standard GEOS-Chem code (in GeosCore/) is now used for the CH4 offline simulation, but in TOMAS it's used for something else.
- Some parameters needed to be declared differently with for simulations with TOMAS.
- Because not all GEOS-Chem users will choose to use TOMAS, we did not want to unnecessarily bog down the code in GeosCore/ with references to TOMAS-specific routines.
All of these concerns could be best solved by keeping parallel copies of the affected routines in the GeosTomas directory.
--Bob Y. 10:36, 27 January 2010 (EST)
Building GEOS-Chem with TOMAS
The VPATH feature of GNU Make is used to simplify the compilation. When GEOS-Chem is compiled with the TOMAS option, the GNU Make utility will search for files in the GeosTomas/ directory first. If it cannot find files there, it will then search the GeosCore/ directory. Thus, if we make a change to a "core" GEOS-Chem routine in the GeosCore/ subdirectory (say in dao_mod.f or diag49_mod.f), then those changes will automatically be applied when you build GEOS-Chem with TOMAS. Thus, we only need to keep in GeosTomas/ separate copies of those files that have to "talk" with TOMAS.
Several new targets were added to the Makefile in the top-level Code/ directory:
#=============================================================================
# Targets for TOMAS aerosol microphysics code (win, bmy, 1/25/10)
#=============================================================================
.PHONY: tomas libtomas exetomas cleantomas
tomas:
@$(MAKE) -C $(GEOSTOM) TOMAS=yes all
libtomas:
@$(MAKE) -C $(GEOSTOM) TOMAS=yes lib
exetomas:
@$(MAKE) -C $(GEOSTOM) TOMAS=yes exe
cleantomas:
@$(MAKE) -C $(GEOSTOM) TOMAS=yes clean
You can build GEOS-Chem with the TOMAS option by typing:
make TOMAS=yes ...
This will automatically do the proper things to build the TOMAS code into GEOS-Chem, such as:
- Adding a -DTOMAS C-preprocessor switch to the FFLAGS compiler flag settings in Makefile_header.mk. This will cause TOMAS-specific areas of code to be turned on.
- Turning off OpenMP parallelization. For now the GEOS-Chem + TOMAS code needs to be run on a single processor. We continue to work on parallelizing the code.
- Calling the Makefile in the GeosTomas/ subdirectory to build the executable. The executable file is now named geostomas in order to denote that the TOMAS code is built in.
The GEOS-Chem + TOMAS has been built on the following compilers
- Intel Fortran compiler v10
- SunStudio 12
--Bob Y. 10:36, 27 January 2010 (EST)
Microphysics Routines
The aerosol microphysics code is largely contained within the file tomas_mod.f. Tomas_mod and its subroutines are modular -- they use all their own internal variables
Aerophys
The aerophys routine is where each individual microphysical process is called within the code. Since H2SO4 is the main condensing species, H2SO4 concentrations are calculated using a pseudo-steady state approach as described in Pierce and Adams, 2009, AS&T. Within this routine, nucleation, condensation, and coagulation are calculated at each time step. Cond_nuc is called for coupled nucleation-condensation. Nucleation schemes can either be binary (Vehkamaki et al 2002) or ternary (Napari et al 2002). There is a switch for this in the variable declarations. For nucleation, a parameterization (Kerminen et al 2004) is used to determine the flux of new particles to the first size bin.
--Dan W. 22:36, 28 January 2010 (EST)
Validation
GC-TOMAS v8-02-05 generally compares very well with observations and other models. Below are some results of benchmarking GC-TOMAS with earlier versions of the model as well as observations
Figure 1: CN10 concentrations predicted by GC-TOMAS v8-02-05 against observations. Descriptions of observational data can be found on p 5454 of Pierce et al, Atmos. Chem. Phys., 7, 2007.
Figure 2: Surface layer CCN concentrations at 0.2% supersaturation averaged over the month of January 2006.
Previous issues now resolved
None known at this time.
Outstanding issues
None known at this time.