Nudging meteorology
This process is WRF-specific but may be useful for your WRF-GC runs. The namelist options described here are also described in the WRF User’s Guide
Grid nudging using input FNL data
Add the following lines to your
namelist.input
, into a new section&fdda
as shown below:
&fdda
grid_fdda = 1, 1, 1,
gfdda_inname = "wrffdda_d<domain>",
gfdda_interval_m = 360, 360, 360,
gfdda_end_h = 9999, 9999, 9999,
io_form_gfdda = 2,
fgdt = 0, 0, 0,
if_no_pbl_nudging_uv = 1, 1, 1,
if_no_pbl_nudging_t = 1, 1, 1,
if_no_pbl_nudging_q = 1, 1, 1,
if_zfac_uv = 1, 1, 1,
k_zfac_uv = 10, 10, 10,
if_zfac_t = 0, 0, 10,
k_zfac_t = 10, 10, 10,
if_zfac_q = 0, 0, 0,
k_zfac_q = 10, 10, 10,
guv = 0.0003, 0.0003, 0.0003,
gt = 0.0003, 0.0003, 0.0003,
gq = 0.0003, 0.0003, 0.0003,
if_ramping = 0,
dtramp_min = 60.0
/
The configuration options you need to change with a brief description are listed below.
grid_fdda
(per-domain): 0 for grid analysis nudging off; 1 for grid analysis nudging on.gfdda_inname
: name of fdda input file (wrffdda_d<domain>
) that will be generated when running real.exe.gfdda_interval_m
(per-domain): time interval (in mins) for NCEP FNL analysis times.gfdda_end_h
(per-domain): time (in hours) to stop nudging after the start of the simulation.io_form_gfdda
: analysis data format (2 for netCDF format).fgdt
(per-domain): calculation frequency (in mins) for analysis nudging; 0 = every time step (recommended).if_no_pbl_nudging_uv/if_no_pbl_nudging_t/if_no_pbl_nudging_q
(per-domain): 0 for nudging in the PBL; 1 for no nudging of uv-winds/air temperature/water vapor in the PBL.if_zfac_uv/if_zfac_t/if_zfac_q
(per-domain): 0 for nudge uv-winds/air temperature/water vapor in all layers; 1 for limit nudging to levels abovek_zfac_uv\k_zfac_t\k_zfac_q
.k_zfac_uv/k_zfac_t/k_zfac_q
(per-domain): model level below which nudging is switched off for uv-winds/air temperature/water vapor.guv/gt/gq
(per-domain): nudging coefficient for uv-winds/air temperature/water vapor (s-1).if_ramping
: 0 for nudging ends as a step function; 1 for ramping nudging down at the end of the period.dtramp_min
: time (in mins) for ramping function.
To change whether winds, air temperature, and/or water vapor are nudged you can change if_no_pbl_nudging_uv
(t
or q
.)
Re-run real.exe. This will generate
wrffdda_d<domain>
files in your run directory.Run wrf.exe.
Analysis nudging using surface and upper-air observations
Downloading surface and upper air observation data in rda.ucar.edu (ds461.0 and ds351.0).
Compiling
obsgrid.exe
andget_rda_data.exe
.
To compile
obsgrid.exe
, please refer to OBSGRID Github. If successful, this will generate the executableobsgrid.exe
.
git clone https://github.com/wrf-model/OBSGRID.git OBSGRID
./configure
./compile
To compile
get_rda_data.exe
, please refer to OBSGRID/util/get_rda_data.f.
cd OBSGRID/util
ifort -FR get_rda_data.f -o get_rda_data.exe
Using
combineSurfaceToObs.sh
to combine the downloaded filesSURFACE_OBS:YYYYMMDDHH
andOBS:YYYYMMDDHH
into new files (e.g.C_OBS:YYYYMMDDHH
). This script is available in Github WRF_Nudging.Using
combineCobsToRdaobs.sh
to combine those new files (C_OBS:YYYYMMDDHH
) intorda_obs
. This script is available in Github WRF_Nudging.Using
get_rda_data.exe
to generate files (OBS:YYYY-MM-DD-HH
) for obsgrid.exe.Setting up the options in configuration file (
namelist.oa
). Here is an example of OBSGRID Namelist for running obsgrid.exe.Running
obsgrid.exe
. This will generate filesmetoa_em*
andwrfsfdda_d01
. Please note thatobsgrid.exe
needs to be run aftermetgrid.exe
. The filesmet_em*
must be available in OBSGRID/ directory.
./obsgrid.exe >& obsgrid.out