Physics and other Parameters for Precipitation

[utkarsh-7]

Hi,
I wanted to run a simulation of a storm for the following region -

With 12km, 6km and 3km spatial resolution.

Currently I am using the following namelist -

&time_control
start_year = 2021, 2021, 2021
start_month = 7, 7, 7
start_day = 09, 09, 09
start_hour = 00, 00, 00
end_year = 2021, 2021, 2021
end_month = 7, 7, 7
end_day = 11, 11 ,11
end_hour = 00, 00, 00
interval_seconds = 10800
input_from_file = .true., .true.,.true.
history_interval = 60, 60, 60
frames_per_outfile = 1000, 1000, 1000
restart = .false.
restart_interval = 7200
io_form_history = 2
io_form_restart = 2
io_form_input = 2
io_form_boundary = 2
start_minute = 0, 0, 0
start_second = 0, 0, 0
end_minute = 0, 0, 0
end_second = 0, 0, 0
nocolons = .true.
/

&domains
time_step = 72
time_step_fract_num = 0
time_step_fract_den = 1
max_dom = 3
e_we = 200, 199, 171
e_sn = 150, 151, 161
e_vert = 33, 33, 33
p_top_requested = 5000
num_metgrid_levels = 34
num_metgrid_soil_levels = 4
dx = 12000.0,6000.0,3000.0
dy = 12000.0,6000.0,3000.0
grid_id = 1, 2, 3
parent_id = 1, 1, 2
i_parent_start = 1, 55, 60
j_parent_start = 1, 38, 40
parent_grid_ratio = 1, 2, 2
parent_time_step_ratio = 1, 2, 2
feedback = 1
smooth_option = 0
sfcp_to_sfcp = .true.
/

&physics
mp_physics = 8, 8, 8,
ra_lw_physics = 4, 4, 4,
ra_sw_physics = 4, 4, 4,
radt = 10, 10, 10,
sf_sfclay_physics = 1, 1, 1,
sf_surface_physics = 2, 2, 2,
bl_pbl_physics = 1, 1, 1,
bldt = 0, 0, 0,
ysu_topdown_pblmix = 1,
cu_physics = 1, 0, 0,
cudt = 0, 0, 0,
icloud = 1,
num_land_cat = 21,
sf_urban_physics = 0, 0, 0,
/

&fdda
/

&dynamics
hybrid_opt = 2,
w_damping = 0,
diff_opt = 1, 1, 1,
km_opt = 4, 4, 4,
diff_6th_opt = 0, 0, 0,
diff_6th_factor = 0.12, 0.12, 0.12,
base_temp = 290.
damp_opt = 3,
zdamp = 5000., 5000., 5000.,
dampcoef = 0.2, 0.2, 0.2
khdif = 0, 0, 0,
kvdif = 0, 0, 0,
non_hydrostatic = .true., .true., .true.,
moist_adv_opt = 2, 2, 2,
scalar_adv_opt = 2, 2, 2,
/

&bdy_control
spec_bdy_width = 5,
specified = .true.
/

&grib2
/

&namelist_quilt
nio_tasks_per_group = 0,
nio_groups = 1,
/

So, for precipitation data what should be the best configuration for the physics parameters or any other parameter which plays a crucial role?

 

[Ming Chen]

WRF performance is often case dependent, and it is hard to tell what options are the best for a specific case. We often run a few tests to determine what options are appropriate.
Your physics options look fine to me. I only have a concern about the nesting ratio, which is better to be an odd number, e.g., 3 or 5. With a netsing ratio of 3, you may also be able to run a two-way nested case instead of the triply nested one.

 

[utkarsh-7]

oh ok!
Do you think running the WRF with even number might affect the accuracy of the output like precipitation, temperature etc. ?

 

[Ming Chen]

This does affect the model performance in a certain way...