stability issue in high resolution (1km)

[turuncu77]

Hi All,

I am trying to run the model (3.8.1) at 1 km resolution (over Black Sea region) and I made two offline nesting (12 km and 3 km, using nest.down) to reach 1 km. 12 km and 3 km simulations are fine and runs without any problem but when I run the model at 1 km it dies after couple of days. I tried to reduce dt as much as possible but result is same. So, i just want to know that what is the best practices to run the model such a high resolution? Is there any specific nameless option that I need to test it? You could find the nemelist that I used as follows for your reference.

Regards,

--- namelist.input ---
&time_control
run_days = 31,
run_hours = 0,
run_minutes = 0,
run_seconds = 0,
start_year = 2012,
start_month = 01,
start_day = 25,
start_hour = 00,
start_minute = 00,
start_second = 00,
end_year = 2012,
end_month = 02,
end_day = 05,
end_hour = 00,
end_minute = 00,
end_second = 00,
interval_seconds = 10800
input_from_file = .true.,
history_interval = 180,
history_outname = "output/wrfout_d<domain>_<date>"
frames_per_outfile = 13000,
restart = .false.,
restart_interval = 10080,
rst_outname = 'output/wrfrst_d<domain>_<date>',
rst_inname = 'output/wrfrst_d<domain>_<date>',
io_form_history = 2
io_form_restart = 2
io_form_input = 2
io_form_boundary = 2
auxinput1_inname = "input/met_em.d<domain>.<date>"
io_form_auxinput4 = 2
auxinput4_inname = "wrflowinp_d<domain>"
auxinput4_interval = 360,
debug_level = 0
/

&domains
time_step = 2,
time_step_fract_num = 0,
time_step_fract_den = 1,
max_dom = 1,
e_we = 1483,
e_sn = 1186,
e_vert = 30,
p_top_requested = 5000,
num_metgrid_levels = 38,
num_metgrid_soil_levels = 4,
dx = 1000,
dy = 1000,
grid_id = 1,
parent_id = 1,
i_parent_start = 1,
j_parent_start = 1,
parent_grid_ratio = 1,
parent_time_step_ratio = 1,
feedback = 0,
smooth_option = 0
/

&physics
mp_physics = 10,
ra_lw_physics = 1,
ra_sw_physics = 1,
radt = 5,
sf_sfclay_physics = 1,
sf_surface_physics = 3,
bl_pbl_physics = 1,
bldt = 0,
cu_physics = 0,
cudt = 1,
isfflx = 1,
ifsnow = 1,
icloud = 1,
surface_input_source = 1,
num_soil_layers = 6,
num_land_cat = 21,
sf_urban_physics = 0,
sst_update = 1,
/

&fdda
/

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

&bdy_control
spec_bdy_width = 12,
spec_zone = 1,
relax_zone = 11,
specified = .true.,
nested = .false.,
/

&grib2
/

&namelist_quilt
nio_tasks_per_group = 0,
nio_groups = 1,
/

 

[meteoadriatic]

Hello, few idas, you can implement them all at once:

1) increase epssm = 0.2, to epssm = 1.0
2) use smooth_cg_topo = true in &domains
3) w_damping = 0, to w_damping = 1,
4) damp_opt = 0, to damp_opt = 3,
5) e_vert = 30, might be bit too low

Also, try to find out if you get CFL violations or something else is problem. If there are CFL violations even when you implement those changes above, then probably your terrain is too rough. You can try avoid rough terrain around domain borders by moving your domain a bit, if that doesn't help maybe additional smoothing in geogrid will.

I hope something of above will help you, good luck