cmip6-to-wrfinterm

CMIP6-to-WRFInterim uses pure python implementation to convert CMIP6 sub-daily output into WRF intermediate files, which are used to drive the WRF model for regional dynamical downscaling usage. Currently, only MPI-ESM-1-2-HR model has been teseted in historical run and SSP1/2/5 scenarios, you may need proper modifications for other model convension.

Installation

Please install python3 using Anaconda3 distribution. Anaconda3 with python3.8 and 3.9 has been deeply tested, lower version of python3 may also work (without testing). If numpy, pandas, scipy, xarray, netcdf4 are properly installed, you may skip the installation step.

While, we recommend to create a new environment in Anaconda and install the requirements.txt:

conda create -n test_c2w python=3.9
conda activate test_c2w
pip install -r requirements.txt

Quick start

python3 run_c2w.py

If you successfully run the above command (it is okay to see some FutureWarnings), you should see CMIP6:2100-01-02_00 and CMIP6:2100-01-02_00 in the ./output folder. Copy or link the two intermidiate files to your WPS folder, prepare your geo_em files and setup your namelist.wps properly, now you are ready to run metgrid.exe and the following WRF procedures.

There is a simple example of namelist.wps and namelist.input covering the East Asian region in the ./sample folder for testing.

If you run the sample case successfully, you are expected to see snapshots of the skin temperature in the initial condition and after 6-hour WRFv4.3 run as shown as above.

Usage

Modify config.ini

When you properly download the MPI-ESM1-2-HR data, First edit the ./conf/config.ini file properly.

[INPUT]
input_root=./sample/ 
model_name=MPI-ESM1-2-HR
exp_id = ssp585
esm_flag=r1i1p1f1
grid_flag=gn
#YYYYMMDDHHMM
cmip_strt_ts = 210001020000
cmip_end_ts = 210001020600
# In hours
cmip_frq=6

[OUTPUT]
#YYYYMMDDHHMM, please seperate your ETL processes if request very long-term simulation
etl_strt_ts = 210001020000
etl_end_ts = 210001020600
output_root = ./output/
output_prefix=CMIP6 

• [INPUT]['input_root'] is the root directory of the CMIP6 data, here it points to the ./sample/ folder.
• [INPUT]['model_name'] is the name of the model. Now only the MPI-ESM-1-2-HR model is supported. This item will guide the script to read the corresponding variable mapping table in ./db/. If you plan to use other models, you need to setup your own variable mapping table (see below).
• [INPUT]['exp_id'] ['esm_flag'] ['grid_flag'] are used to form the netCDF file name.
• [INPUT]['cmip_strt_ts'] and [INPUT]['cmip_end_ts'] are the start and end time of the CMIP6 data.
• [OUTPUT]['etl_strt_ts'] and [OUTPUT]['etl_end_ts'] are the start and end time of your desired ETL period.

After you have edited the config.ini file, you can run the script again for your desired period. The intemediate files will be generated in the [OUTPUT]['output_root'] folder. Note that for MPI-ESM-1-2-HR, the soil properties between 10-200cm is not provided by the model and we overwrote it by 0-10cm soil properties, a special type mark of 2d-soilr is provided in the varaible mapping table. You may need long-term (~1-month) spin-up run if your research requests accurate soil properties.

[OPTIONAL] Modify ./db/${MODEL_NAME}.csv

./db/${MODEL_NAME}.csv records the model-specified variable mapping table. If you plan to use other models, you need to setup your own variable mapping table.

src_v,aim_v,units,type,lvlmark,desc
ta,TT,K,3d,PlevPt,3-d air temperature
hus,SPECHUMD,kg kg-1,3d,PlevPt,3-d specific humidity
ua,UU,m s-1,3d,PlevPt, 3-d wind u-component
va,VV,m s-1,3d,PlevPt, 3-d wind v-component
zg,GHT,m,3d,PlevPt, 3-d geopotential height
ps,PSFC,Pa,2d,Lev, Surface pressure
tas,TT,K,2d,PlevPt, 2-m temperature
uas,UU,m s-1,2d,PlevPt, 10m wind u-component
vas,VV,m s-1,2d,PlevPt, 10m wind v-component
ts,SKINTEMP, K,2d,PlevPt, Skin temperature
ts,SST, K,2d,PlevPt, sea surface temperature
psl,PMSL,Pa,2d,PlevPt, Mean sea-level pressure
huss,SPECHUMD, kg kg-1,2d,PlevPt, 2-m relative humidity
mrsos,SM000010, m3/m-3,2d-soil,PlevPt, 0-10 cm soil moisture
tsl,ST000010,K,2d-soil,PlevPt, 0-10 cm soil temp 
mrsos,SM010200, m3/m-3,2d-soilr,PlevPt, 10-200 cm soil moisture
tsl,ST010200,K,2d-soilr,PlevPt, 10-200 cm soil temp 

• src_v is the name of the variable in the CMIP6 data, which is also used to form the netCDF file name.
• aim_v is the name of the variable archived in WRF intermidiate file, which is used by metgrid.exe.
• units is the unit of the variable.
• type denotes the type of the variable. 3d means 3-d variable, 2d means 2-d variable, 2d-soil means 2-d variable in the soil layer. Note that for MPI-ESM-1-2-HR, the soil properties between 10-200cm is not provided by the model and we overwrote it by 0-10cm soil, a special type mark of 2d-soilr is provided here.
• lvlmark is the level mark of the variable. PlevPt means the variable is a 3-d variable with pressure level.
• desc is the description of the variable.

[Advanced] cmip_handler.py

The core of the converter is cmip_handler.py. It is a Python module that handles the CMIP6 data and converts it to WRF intermidiate file. The module first load CMIP6 data according to the config.ini file, then it interpolates to regular latXlon mesh. Finally it convert the data to WRF intermidiate file. The module includes the following functions and classes:

Functions:
    gen_wrf_mid_template():
        Generate a WRF-Mid template dict for the WRF-Intermediate data.

    write_record(out_file, slab_dic):
        Write a record to a WRF intermediate file
    --------------------
    Classes:
    CMIPHandler():
        Construct CMIP Handler 

        Methods
        -------
        __init__:   initialize CMIP Handler with config and loading data
        interp_data: interpolate data to common mesh
        write_wrfinterm: write wrfinterm file

[Appendix] Fetch Input Files

According to WRF Users Guide (v4.2), P3-36:

Required Meteorological Fields for Running WRF

In order to successfully initialize a WRF simulation, the real.exe pre-processor requires a minimum set of meteorological and land-surface fields to be present in the output from the metgrid.exe program. Accordingly, these required fields must be available in the intermediate files processed by metgrid.exe.

CMIP6 data can be downloaded from the LLNL interface, after cross-check the variable list from MPI-ESM-1-2-HR and the WRF required variables, we have the following table:

You may setup your own variable mapping table in ./db/${MODEL_NAME}.csv if you want to use other models.

Any question, please contact Zhenning LI (zhenningli91@gmail.com)