Spurious upper atmospheric waves

Anything related to the idealized simulations in WRF.

Spurious upper atmospheric waves

Postby harrisonli » Thu Jun 25, 2015 10:01 am

Hi everyone-

I've been running 14-day 2-D ideal simulations of the Arctic during polar night, but there appears to be a spurious wave pattern that develops between 100 and 200 hPa in the zonal and vertical wind fields. I've tried modifying the Rayleigh damping layer thickness, increasing the damping coefficient, adding additional vertical levels to the top, and reducing the model timestep all to no avail. See the attached animation at around 8 days in (1:35 into the video) for what I'm talking about; it is from a run with the following namelist values:

&time_control
run_days = 14,
run_hours = 0,
run_minutes = 0,
run_seconds = 0,
start_year = 0001,
start_month = 01,
start_day = 01,
start_hour = 00,
start_minute = 00,
start_second = 00,
end_year = 0001,
end_month = 01,
end_day = 15,
end_hour = 00,
end_minute = 00,
end_second = 00,
history_interval = 5,
frames_per_outfile = 8760,
restart = .false.,
restart_interval = 10080,
io_form_history = 2
io_form_restart = 2
io_form_input = 2
io_form_boundary = 2
debug_level = 0
/

&domains
time_step = 3,
time_step_fract_num = 0,
time_step_fract_den = 1,
max_dom = 1,
s_we = 1,
e_we = 71,
s_sn = 1,
e_sn = 2,
s_vert = 1,
e_vert = 55,
dx = 500,
dy = 500,
eta_levels = 1.000, 0.998, 0.994, 0.989, 0.982,
0.975, 0.966, 0.957, 0.947, 0.936,
0.924, 0.911, 0.898, 0.884, 0.870,
0.854, 0.839, 0.822, 0.805, 0.787,
0.769, 0.750, 0.731, 0.711, 0.691,
0.670, 0.649, 0.627, 0.605, 0.582,
0.558, 0.535, 0.510, 0.486, 0.461,
0.435, 0.409, 0.382, 0.355, 0.328,
0.300, 0.272, 0.243, 0.214, 0.185,
0.155, 0.125, 0.100, 0.080, 0.060,
0.045, 0.030, 0.020, 0.010, 0.000,
ztop = 34750.,
/


&physics
mp_physics = 2,
icloud = 1,
ra_lw_physics = 4,
ra_sw_physics = 4,
radt = 2,
sf_sfclay_physics = 1,
sf_surface_physics = 1,
bl_pbl_physics = 1,
bldt = 0,
cu_physics = 0,
cudt = 0,
isfflx = 1,
num_soil_layers = 5,
rrtmg_co2vmr = 300.0,
atm_qflux = 0.0,
omlcall = 1,
oml_hml0 = 0.05,
oml_gamma = 0.14,
oml_qflux = 00.0,
bucket_mm = 100.0,
bucket_J = 1.e9,
/

&fdda
/

&dynamics
rk_ord = 3,
ncol_urelax = 1,
ncol_u0 = 5.,
ncol_du_vert = 0.,
ncol_tau_u = 86400.,
diff_opt = 2,
km_opt = 1,
damp_opt = 2,
dampcoef = .01,
zdamp = 15000.,
khdif = 1,
kvdif = 1,
smdiv = 0.1,
emdiv = 0.01,
epssm = 0.1,
time_step_sound = 6,
h_mom_adv_order = 5,
v_mom_adv_order = 3,
h_sca_adv_order = 5,
v_sca_adv_order = 3,
mix_full_fields = .true.,
non_hydrostatic = .true.,
moist_adv_opt = 1, 1, 1,
scalar_adv_opt = 1, 1, 1,
chem_adv_opt = 1, 1, 1,
tke_adv_opt = 1, 1, 1,
/

&bdy_control
periodic_x = .true.,
symmetric_xs = .false.,
symmetric_xe = .false.,
open_xs = .false.,
open_xe = .false.,
periodic_y = .true.,
symmetric_ys = .false.,
symmetric_ye = .false.,
open_ys = .false.,
open_ye = .false.,
/

&grib2
/

&namelist_quilt
nio_tasks_per_group = 0,
nio_groups = 1,
/

Does anyone have any ideas as to how to get rid of this? Thanks!
harrisonli
 
Posts: 1
Joined: Thu Jun 25, 2015 12:45 am

Re: Spurious upper atmospheric waves

Postby Phillip » Mon Jun 29, 2015 8:52 am

I can't see any animation :/ Am I missing something?

Concerning the waves, what is their wavelength with respect to your grid size? Is it for example exactly two or six times your grid spacing? If so it might be a numerical artifact. Those can be filtered by using numerical diffusion, but that lowers the effective resolution of the model and increases computation time. I'm not an expert on the topic, so I can't offer much help other than this.

Have a look at the WRF manual where 6th order diffusion is described. That should at least be able to take care of waves which ave a wavelength of 2dx.
Phillip
 
Posts: 44
Joined: Thu Jul 19, 2012 3:29 am


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