In order to set up the workflow and generate an experiment with the SRW Application, the user must choose between various predefined FV3-LAM grids or generate a user-defined grid. At this time, full support is only provided to those using one of the four predefined grids supported in the v2.1.0 release, but other predefined grids are available (see Section 184.108.40.206 for more detail). Preliminary information is also provided at the end of this chapter describing how users can leverage the SRW App workflow scripts to generate their own user-defined grid and/or adjust the number of vertical levels in the grid. Currently, this feature is not fully supported and is “use at your own risk.”
3.3.1. Predefined Grids
The SRW App v2.1.0 release includes four predefined limited area model (LAM) grids. To select a supported predefined grid, the
PREDEF_GRID_NAME variable within the
workflow: section of the
config.yaml script must be set to one of the following four options:
These four options are provided for flexibility related to compute resources and supported physics options. Other predefined grids are listed here. The high-resolution 3-km CONUS grid generally requires more compute power and works well with three of the five supported physics suites (see Table 3.2). Low-resolution grids (i.e., 13-km and 25-km domains) require less compute power and should generally be used with the other supported physics suites:
In theory, it is possible to run any of the supported physics suites with any of the predefined grids, but the results will be more accurate and meaningful with appropriate grid/physics pairings.
The predefined CONUS grids follow the naming convention (e.g.,
RRFS_CONUS_*km) of the 3-km version of the continental United States (CONUS) grid being tested for the Rapid Refresh Forecast System (RRFS). RRFS will be a convection-allowing, hourly-cycled, FV3-LAM-based ensemble planned for operational implementation in 2025. All four supported grids were created to fit completely within the High Resolution Rapid Refresh (HRRR) domain to allow for use of HRRR data to initialize the SRW App.
220.127.116.11. Predefined 3-km CONUS Grid
The 3-km CONUS domain is ideal for running the
FV3_RRFS_v1beta physics suite, since this suite definition file (SDF) was specifically created for convection-allowing scales and is the precursor to the operational physics suite that will be used in RRFS. The 3-km domain can also be used with the
FV3_WoFS physics suites, which likewise do not include convective parameterizations. In fact, the
FV3_WoFS physics suite is configured to run at 3-km or less and could therefore run with even higher-resolution user-defined domains if desired. However, the
FV3_RAP suites generally should not be used with the 3-km domain because the cumulus physics used in those physics suites is not configured to run at the 3-km resolution.
The boundary of the
RRFS_CONUS_3km domain is shown in Figure 3.2 (in red), and the boundary of the write-component grid sits just inside the computational domain (in blue). This extra grid is required because the post-processing utility (UPP) is unable to process data on the native FV3 gnomonic grid (in red). Therefore, model data are interpolated to a Lambert conformal grid (the write component grid) in order for the UPP to read in and correctly process the data.
While it is possible to initialize the FV3-LAM with coarser external model data when using the
RRFS_CONUS_3km domain, it is generally advised to use external model data (such as HRRR or RAP data) that has a resolution similar to that of the native FV3-LAM (predefined) grid.
18.104.22.168. Predefined SUBCONUS Grid Over Indianapolis
SUBCONUS_Ind_3km grid covers only a small section of the CONUS centered over Indianapolis. Like the
RRFS_CONUS_3km grid, it is ideally paired with the
FV3_WoFS physics suites, since these are all convection-allowing physics suites designed to work well on high-resolution grids.
22.214.171.124. Predefined 13-km Grid
RRFS_CONUS_13km grid (Fig. 3.4) covers the full CONUS. This grid is meant to be run with the
FV3_RAP physics suites. These suites use convective parameterizations, whereas the other supported suites do not. Convective parameterizations are necessary for low-resolution grids because convection occurs on scales smaller than 25-km and 13-km.
126.96.36.199. Predefined 25-km Grid
The final predefined CONUS grid (Fig. 3.5) uses a 25-km resolution and
is meant mostly for quick testing to ensure functionality prior to using a higher-resolution domain.
However, for users who would like to use the 25-km domain for research, the
FV3_GFS_v16 SDF is recommended for the reasons mentioned above.
Ultimately, the choice of grid is experiment-dependent and resource-dependent. For example, a user may wish to use the
FV3_GFS_v16 physics suite, which uses cumulus physics that are not configured to run at the 3-km resolution. In this case, the 13-km or 25-km domain options are better suited to the experiment. Users will also have fewer computational constraints when running with the 13-km and 25-km domains, so depending on the resources available, certain grids may be better options than others.
3.3.2. Creating User-Generated Grids
While the four supported predefined grids are ideal for users just starting out with the SRW App, more advanced users may wish to create their own predefined grid for testing over a different region and/or with a different resolution. Creating a user-defined grid requires knowledge of how the SRW App workflow functions. In particular, it is important to understand the set of scripts that handle the workflow and experiment generation (see Figure 2.3 and Figure 2.4). It is also important to note that user-defined grids are not a supported feature of the current release; however, information is being provided for the benefit of the FV3-LAM community.
With those caveats in mind, this section provides instructions for adding a new predefined grid to the FV3-LAM
workflow that will be generated using the “ESGgrid” method (i.e., using the
in the UFS_UTILS repository, where ESG stands for “Extended Schmidt Gnomonic”). We assume here that the grid to be generated covers a domain that (1) does not contain either of the poles and (2) does not cross the -180 deg –> +180 deg discontinuity in longitude near the international date line. More information on the ESG grid is available here. Instructions for domains that do not have these restrictions will be provided in a future release.
The steps to add such a grid to the workflow are as follows:
Choose the name of the grid. For the purposes of this documentation, the grid will be called “NEW_GRID”.
Add NEW_GRID to the array
ufs-srweather-app/ush/predef_grid_params.yaml, add a stanza describing the parameters for NEW_GRID. An example of such a stanza is given below. For descriptions of the variables that need to be set, see Sections 188.8.131.52 and 3.1.3.
To run a forecast experiment on NEW_GRID, start with a workflow configuration file for a successful experiment (e.g.,
config.community.yaml, located in the
ufs-srweather-app/ush subdirectory), and change the line for
PREDEF_GRID_NAME in the
workflow: section to
Then, load the workflow environment, specify the other experiment parameters in
config.community.yaml, and generate a new experiment/workflow using the
generate_FV3LAM_wflow.py script (see Section 2.4.3 for details).
184.108.40.206. Code Example
The following is an example of a code stanza for “NEW_GRID” to be added to
# #--------------------------------------------------------------------- # # Stanza for NEW_GRID. This grid covers [description of the # domain] with ~[size]-km cells. # #--------------------------------------------------------------------- "NEW_GRID": # The method used to generate the grid. This example is specifically for the "ESGgrid" method. GRID_GEN_METHOD: "ESGgrid" # ESGgrid parameters: ESGgrid_LON_CTR: -97.5 ESGgrid_LAT_CTR: 38.5 ESGgrid_DELX: 25000.0 ESGgrid_DELY: 25000.0 ESGgrid_NX: 200 ESGgrid_NY: 112 ESGgrid_PAZI: 0.0 ESGgrid_WIDE_HALO_WIDTH: 6 # Forecast configuration parameters: DT_ATMOS: 40 LAYOUT_X: 5 LAYOUT_Y: 2 BLOCKSIZE: 40 # Parameters for the write-component (aka "quilting") grid. QUILTING: WRTCMP_write_groups: 1 WRTCMP_write_tasks_per_group: 2 WRTCMP_output_grid: "lambert_conformal" WRTCMP_cen_lon: -97.5 WRTCMP_cen_lat: 38.5 WRTCMP_lon_lwr_left: -121.12455072 WRTCMP_lat_lwr_left: 23.89394570 # Parameters required for the Lambert conformal grid mapping. WRTCMP_stdlat1: 38.5 WRTCMP_stdlat2: 38.5 WRTCMP_nx: 197 WRTCMP_ny: 107 WRTCMP_dx: 25000.0 WRTCMP_dy: 25000.0
The process above explains how to create a new predefined grid, which can be used more than once. If a user prefers to create a custom grid for one-time use, the variables above can instead be specified in
PREDEF_GRID_NAME can be set to a null string. In this case, it is not necessary to modify
predef_grid_params.yaml. Users can view an example configuration file for a custom grid here.
3.3.3. Changing the Number of Vertical Levels
The four supported predefined grids included with the SRW App are configured to run with 65 levels by default. However, advanced users may wish to vary the number of vertical levels in the grids they are using, whether these be the predefined grids or a user-generated grid. Varying the number of vertical levels requires knowledge of how the SRW App interfaces with the UFS Weather Model (WM) and preprocessing utilities. It is also important to note that user-defined vertical levels are not a supported feature at present; information is being provided for the benefit of the FV3-LAM community, but user support for this feature is limited. With those caveats in mind, this section provides instructions for creating a user-defined vertical coordinate distribution on a regional grid.
Users will need to determine
bk values, which are used to define the vertical levels. The UFS WM uses a hybrid vertical coordinate system, which moves from purely sigma levels near the surface to purely isobaric levels near the top of the atmosphere (TOA). The equation \(pk=ak+bk*ps\) (where
ps is surface pressure) is used to derive the pressure value at a given level. The
ak values define the contribution from the purely isobaric component of the hybrid vertical coordinate, and the
bk values are the contribution from the sigma component. When
bk are both zero, it is the TOA (pressure is zero). When
bk is 1 and ak is 0, it is a purely sigma vertical coordinate surface, which is the case near the surface (the first model level).
vcoord_gen tool from UFS_UTILS can be used to generate
bk values, although users may choose a different tool if they prefer. The program can output a text file containing
bk values for each model level, which will be used by
chgres_cube in the
make_lbcs_* tasks to generate the initial and lateral boundary conditions from the external data.
Users can find
vcoord_gen technical documentation here and scientific documentation here. Since UFS_UTILS is part of the SRW App, users can find and run the UFS_UTILS
vcoord_gen tool in their
ufs-srweather-app/exec directory. To run
vcoord_gen within the SRW App:
cd /path/to/ufs-srweather-app/exec ./vcoord_gen > /path/to/vcoord_gen_outfile.txt
Users should modify the output file path to save the output file in the desired location. In the SRW App, the default file defining vertical levels is named
global_hyblev.txt and contains the default 65 levels. By convention, users who create a new vertical coodinate distribution file often append this file name with
LXXX for their number of levels (e.g.,
global_hyblev.L128.txt). Configuration files are typically placed in the
parm directory. For example, users might run:
cd /path/to/ufs-srweather-app/exec ./vcoord_gen > /Users/Jane.Smith/ufs-srweather-app/parm/global_hyblev.L128.txt
vcoord_gen starts, it will print a message telling users to specify certain variables for
For an experiment using 128 vertical levels, users might then input:
Enter, the program will print a
pmin value (e.g.,
pmin= 50392.6447810470) and save the output file in the designated location. Based on the default values used above, the contents of the file should look like this:
2 128 0.000 1.00000000 0.000 0.99752822 0.000 0.99490765 0.029 0.99212990 0.232 0.98918511 0.810 0.98606254 1.994 0.98275079 4.190 0.97923643 8.287 0.97550087 15.302 0.97152399 26.274 0.96728509 42.274 0.96276297 64.392 0.95793599 93.740 0.95278208 131.447 0.94727885 178.651 0.94140368 236.502 0.93513378 306.149 0.92844637 388.734 0.92131872 485.392 0.91372837 597.235 0.90565322 725.348 0.89707176 870.778 0.88796321 1034.524 0.87830771 1217.528 0.86808662 1420.661 0.85728262 1644.712 0.84588007 1890.375 0.83386518 2158.238 0.82122630 2448.768 0.80795416 2762.297 0.79404217 3099.010 0.77948666 3458.933 0.76428711 3841.918 0.74844646 4247.633 0.73197127 4675.554 0.71487200 5124.949 0.69716312 5594.876 0.67886334 6084.176 0.65999567 6591.468 0.64058751 7115.147 0.62067071 7653.387 0.60028151 8204.142 0.57946049 8765.155 0.55825245 9333.967 0.53670620 9907.927 0.51487434 10484.208 0.49281295 11059.827 0.47058127 11631.659 0.44824125 12196.468 0.42585715 12750.924 0.40349506 13291.629 0.38122237 13815.150 0.35910723 14318.040 0.33721804 14796.868 0.31562289 15248.247 0.29438898 15668.860 0.27358215 16055.485 0.25326633 16405.020 0.23350307 16714.504 0.21435112 16981.137 0.19586605 17202.299 0.17809988 17375.561 0.16110080 17498.697 0.14491294 17569.698 0.12957622 17586.772 0.11512618 17548.349 0.10159397 17453.084 0.08900629 17299.851 0.07738548 17088.325 0.06674372 16820.937 0.05706358 16501.018 0.04831661 16132.090 0.04047056 15717.859 0.03348954 15262.202 0.02733428 14769.153 0.02196239 14242.890 0.01732857 13687.727 0.01338492 13108.091 0.01008120 12508.519 0.00736504 11893.639 0.00518228 11268.157 0.00347713 10636.851 0.00219248 10004.553 0.00127009 9376.141 0.00065078 8756.529 0.00027469 8150.661 0.00008141 7563.494 0.00001018 7000.000 0.00000000 6463.864 0.00000000 5953.848 0.00000000 5468.017 0.00000000 5004.995 0.00000000 4563.881 0.00000000 4144.164 0.00000000 3745.646 0.00000000 3368.363 0.00000000 3012.510 0.00000000 2678.372 0.00000000 2366.252 0.00000000 2076.415 0.00000000 1809.028 0.00000000 1564.119 0.00000000 1341.538 0.00000000 1140.931 0.00000000 961.734 0.00000000 803.164 0.00000000 664.236 0.00000000 543.782 0.00000000 440.481 0.00000000 352.894 0.00000000 279.506 0.00000000 218.767 0.00000000 169.135 0.00000000 129.110 0.00000000 97.269 0.00000000 72.293 0.00000000 52.984 0.00000000 38.276 0.00000000 27.243 0.00000000 19.096 0.00000000 13.177 0.00000000 8.947 0.00000000 5.976 0.00000000 3.924 0.00000000 2.532 0.00000000 1.605 0.00000000 0.999 0.00000000 0.000 0.00000000
220.127.116.11. Configure the SRW App
To use the new
bk file to define vertical levels in an experiment, users will need to modify the input namelist file (
input.nml.FV3) and their configuration file (
The FV3 namelist file,
input.nml.FV3, is located in
ufs-srweather-app/parm. Users will need to update the
npz variables in this file. For
n vertical levels, users should set
npz=n-1. For example, a user who wants 128 vertical levels would set
npz as follows:
&external_ic_nml levp = 128 &fv_core_nml npz = 127
Additionally, check that
external_eta = .true..
Keep in mind that levels and layers are not the same. In UFS code,
levp is the number of vertical levels, and
npz is the number of vertical levels without TOA. Thus,
npz is equivalent to the number of vertical layers. For
v vertical layers, set
levp=v+1. Use the value of
levp as the number of vertical levels when generating
To use the text file produced by
vcoord_gen in the SRW App, users need to set the
VCOORD_FILE variable in their
config.yaml file. Normally, this file is named
global_hyblev.l65.txt and is located in the
fix_am directory on Level 1 systems, but users should adjust the path and name of the file to suit their system. For example, in
task_make_ics: VCOORD_FILE: /Users/Jane.Smith/ufs-srweather-app/parm/global_hyblev.L128.txt task_make_lbcs: VCOORD_FILE: /Users/Jane.Smith/ufs-srweather-app/parm/global_hyblev.L128.txt
Configure other variables as desired and generate the experiment as described in Section 2.4.3.