Running WRF-GC

The process of running WRF-GC is very similar to that for running WRF-Chem.

Running the WPS

First, one must run the WRF Preprocessing System (WPS) to prepare the input data for driving WRF. The modeling configuration options are defined in the "namelist.wps" file. Please refer to the WRF User's Guide for more detail.

Step 1: Defining model domains with geogrid

In the "geogrid" namelist record, the projection of the simulation domain is defined. As of WRF-GC version 0.1, only two sets of map projections and specified parameters are supported:

• Mercator /'mercator' (truelat1)

• Unrotated regular latitude-longitude /'lat-lon' (pole_lat, pole_lon, stand_lon)

An example of "geogrid" namelist records in the "namelist.wps" file is shown below:

       &share 
        wrf_core = 'ARW',
        max_dom = 1,
        start_date = '2015-01-18_00:00:00',
        end_date   = '2015-01-28_00:00:00',
        interval_seconds = 21600
        io_form_geogrid = 2,
       /

       &geogrid
        parent_id         =   1,   
        parent_grid_ratio =   1,   
        i_parent_start    =   1,  
        j_parent_start    =   1,  
        e_we              =  245,
        e_sn              =  181, 
        geog_data_res = 'gtopo_2m+usgs_2m+nesdis_greenfrac+2m',
        dx = 27000,
        dy = 27000,
        map_proj = 'mercator',
        ref_lat   =  35.0,
        ref_lon   =  105.0,
        truelat1  =  30.0,
        stand_lon =  105.0,
        geog_data_path = '/users/wrf/data/geog'
       /

Step 2: Downloading and extracting meteorological data from GRIB files with ungrib

For a 'real' WRF case, you need to download the meteorological data that will be used as the initial and boundary condition to drive WRF. You have a number of choices. We use the NCEP FNL reanalyses product.

Available free datasets for driving WRF

An example of "ungrib" namelist records in the "namelist.wps" file is shown below:

       &share 
        wrf_core = 'ARW',
        max_dom = 1,
        start_date = '2015-01-18_00:00:00',
        end_date   = '2015-01-28_00:00:00',
        interval_seconds = 21600
        io_form_geogrid = 2,
       /

       &ungrib
        out_format = 'WPS',
        prefix = 'FILE',
       /

Step 3: Horizontally interpolating meteorological data with metgrid

An example of "metgrid" namelist records in the "namelist.wps" file is shown below:

       &share 
        wrf_core = 'ARW',
        max_dom = 1,
        start_date = '2015-01-18_00:00:00',
        end_date   = '2015-01-28_00:00:00',
        interval_seconds = 21600
        io_form_geogrid = 2,
       /

       &metgrid
       fg_name = 'FILE'
       io_form_metgrid = 2,
       /

Preparing GEOS-Chem shared data directories

The GEOS-Chem shared data directories contain many large files necessary for the WRF-GC. Please Set up the top-level root directory for GEOS-Chem shared data, which is called ExtData. Please create the /dir/to/data/ExtData and set your directories in the "input.geos" file:

       Root data directory : /dir/to/data/ExtData

The ExtData directory structure cotains two subdirectories:

- CHEM_INPUT: Non-emissions data for GEOS-Chem chemistry modules

• Download the CHEM_INPUT data directories via anonymous FTP from the Harvard data directory archive (ftp.as.harvard.edu). Please refer to : http://wiki.seas.harvard.edu/geos-chem/index.php/Downloading_GEOS-Chem_source_code_and_data

- HEMCO: Emissions inventories for the HEMCO emissions component

• Download the HEMCO data directories with a pakeage provided by GEOS-Chem Support Team. Please refer to : http://wiki.seas.harvard.edu/geos-chem/index.php/HEMCO_data_directories#Downloading_the_HEMCO_data_directories

• Set the HEMCO data directory in the "HEMCO_Config.rc" file

       Root : /dir/to/data/ExtData/HEMCO

Emissions for WRF-GC

Preparing emission files is not required. WRF-GC uses the Harvard-NASA Emissions Component (HEMCO) with on-line regridding. Configure HEMCO refer to the "HEMCO_Config.rc" file inside the run directory for WRF. For more information on HEMCO data directories, please refer to the GEOS-Chem wiki:

Preparing chemical initial/boundary condition data

Chemical initial and boundary condition data are used output from global simulation MOZART-4/GEOS-5 similar to WRF-Chem. Please download the data from :

• https://www.acom.ucar.edu/wrf-chem/mozart.shtml

The Mozart data are processed by the WRF-Chem processor called mozbc. Please download the mozbc utility, including instructions and input files from :

• https://www.acom.ucar.edu/wrf-chem/download.shtml

Running WRF-GC

To Configure WRF-GC, you need to edit three files inside the WRF run directory.

- HEMCO_Config.rc (Please refer to: http://wiki.seas.harvard.edu/geos-chem/index.php/GEOS-Chem_Input_Files#The_HEMCO_Config.rc_file)

• HEMCO_Config.rc file contains a set of switches to enable and disable emission inventories, such as:

      # ExtNr ExtName           on/off  Species
      0       Base              : on    *
          --> HEMCO_RESTART     :       false
          --> AEIC              :       true
          --> BIOFUEL           :       true
      ... etc not shown here ...

• Errors with HEMCO component when running a simulation are output into a log file called "HEMCO.log".

- input.geos (Please refer to : http://wiki.seas.harvard.edu/geos-chem/index.php/GEOS-Chem_Input_Files)

• Simulation Menu (except Root data directory) and Timestep Menu in input.geos can be safely ignored.

• Determine the Advected Species Menu, Transport Menu, Convection Menu, Emission Menu, Aerosol Menu, Deposition Menu and Chemistry Menu according to your specific simulation.

• Other Menus in "input.geos" can be safely ignored.

- namelist.input

....available soon....

To run WRF-GC, use the distributed-memory parallel version of WRF's real.exe and wrf.exe, like -

       mpirun -np 6 ./wrf.exe

To monitor output from WRF&GEOS-Chem, you can tail the "rsl.out.000" file:

       tail -f rsl.out.0000

Output from WRF&GEOS-Chem are unified into the WRF output format (NetCDF Classic) files starting with wrfout.