Aerosol/Chemical Data Assimilation
Aerosol/Chemical data assimilation capability is added in version 4.3 and updated in version 4.4 (WRFDA Updates for 4.4). Currently it allows the assimilation of 6 types of surface measurements (PM2.5, PM10, O3, CO, NO2, SO2) with 3DVAR, which can provide the analyzed initial conditions for WRF-Chem. This new capability is documented by Sun et al. (2020) and Ha (2022).
Sun, W., Liu, Z., Chen, D., Zhao, P., and Chen, M., 2020: Development and application of the WRFDA-Chem three-dimensional variational (3DVAR) system: aiming to improve air quality forecasting and diagnose model deficiencies,
Atmos. Chem. Phys., 20, 9311-9329.
Ha, S., 2022: Implementation of aerosol data assimilation in WRFDA (v4.0.3) for WRF-Chem (v3.9.1) using the RACM/MADE-VBS scheme, Geosci. Model Dev., 15, 1769–1788,
Implementation of aerosol data assimilation in WRFDA (v4.0.3) for WRF-Chem (v3.9.1) using the RACM/MADE-VBS scheme.
Here we give some information about how to compile and configure WRFDA for this capability. The four gas-phase analysis variables include O3, CO, NO2 and SO2. For aerosols, it works with GOCART, MOSAIC (4 bin), and MADE/VBS aerosol scheme in WRF-Chem, consisting of 15, 32 or 35 species, respectively.
To compile 3DVAR with aerosol/chemical DA capability, following the commands below:
setenv WRF_CHEM 1
./configure wrfda
./compile all_wrfvar
The executable is still da_wrfvar.exe, but now it can take WRF-Chem’s initial condition file as the background (i. e., the ‘fg’ file) and perform the aerosol/chemical analysis in addition to the usual function for meteorological analysis. All related settings are in a new namelist section named
wrfvarchem. Each namelist parameter is explained below.
&wrfvarchem
chem_cv_options= 10/20/108, control variables are 4 gas + GOCART, MOSAIC or MADE/VBS
aerosol variables. Default is 0, no aerosol/chemical DA.
chemicda_opt=1/2/3/4/5, assimilate pm2.5/pm10/pm2.5+pm10/co+o3+so2+no2/6-species.
Default is 1.
var_scaling12=1.0, 1.0, …, array with a dimension of 45*max_outer_iterations, inflation factors of
chemical background error variances of aerosol/gas analysis variables at different
outer loops. Default values are 1 (no inflation).
len_scaling12=1.0, 1.0, …, arrary with a dimension of 45*max_outer_iterations, inflation factors of
chemical background error length scales. Default values is 1.
use_chemic_surfobs = .true., Default is true, read in
ob_chemsfc.ascii file that includes 6 types of
observations at analysis time. Please refer to var/da/da_obs_io/da_read_obs_chem_sfc.inc for format.
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The standard GEN_BE package included in WRFDA cannot obtain the background error statistics for aerosol/chemical variables, users will need to use GitHub - wrf-model/GENBE_2.0: Repository for the new stand-alone GEN_BE capability for WRFDA. to generate a be.dat file that contains the background errors of chemical variables. Please refer to the online commit message for its use.
A testcase is provided in
Index of /wrf/users/wrfda/chemda_testcase. We have no resource to provide the assistance of this capability for users’ own applications without funding support.
