[Wrf-users] Exceeded cfl=2 at the corners of the domain
Kevin Matthew Nuss
weather at nusculus.com
Wed Mar 30 20:55:40 MDT 2016
Those dreaded CFL errors! We all feel your pain.
Having them that bad in a North American domain makes me think you have
undesirable input data for the initialization. You already tried shorter
time steps, try an earlier start time (8 hours maybe) as a test.
I'm over simplifying, but CFL errors mean you have too much vertical
velocity for the height of your grid cells. Having mountains near your
domain boundaries make this happen more often. But with a continental
domain, your corners are probably over the ocean. Maybe the input has
strangely warm water causing vertical velocities. Sometimes just changing
the eppsm value (read your WRF namelist documentation) from 0.1 to 0.3, or
anything else BELOW 1.0, will magically fix the problem. If this was not
happening immediately after the start, I would suggest adding some vertical
dampening. I have longer versions of these ideas here:
http://www.nusculus.com/wrf-errors
I'm sorry to not have any absolute answers but maybe this will give you
something else to try.
best wishes
Kevin
On Wed, Mar 30, 2016 at 8:04 PM, Wang, Yaoping <
wang.3866 at buckeyemail.osu.edu> wrote:
> Hello,
>
>
> I am new to WRF and am setting up a run over the North American domain at
> 30km resolution. But I keep getting "exceeded cfl=2". After testing various
> time steps it seems that the error keep occurring at the corners of my
> domain. I also checked the wind speeds and divergence in the input
> meteorological data, but did not find any clear outlier models. Could
> anyone give some suggestions as to what can be done to solve the problem?
>
>
> *The trials and errors: *
>
> *time step = 180s*
>
> d01 1967-01-01_00:00:00 5537 points exceeded cfl=2 in domain d01
> at time 1967-01-01_00:00:00 hours
> d01 1967-01-01_00:00:00 MAX AT i,j,k: 283 42
> 2 vert_cfl,w,d(eta)= 2.4396536E+07 NaN 9.9999905E-03
> d01 1967-01-01_00:00:00 1906 points exceeded cfl=2 in domain d01
> at time 1967-01-01_00:00:00 hours
> d01 1967-01-01_00:00:00 MAX AT i,j,k: 21 190
> 20 vert_cfl,w,d(eta)= 1102.228 -6444.851 3.5938144E-02
> Timing for main: time 1967-01-01_00:03:00 on domain 1: 15.48090
> elapsed seconds
>
>
> *time step = 90s*
>
> d01 1967-01-01_00:00:00 6080 points exceeded cfl=2 in domain d01
> at time 1967-01-01_00:00:00 hours
> d01 1967-01-01_00:00:00 MAX AT i,j,k: 283 46
> 29 vert_cfl,w,d(eta)= 6955.001 -1.8047905E+15 9.2214663E-03
> d01 1967-01-01_00:00:00 1969 points exceeded cfl=2 in domain d01
> at time 1967-01-01_00:00:00 hours
> d01 1967-01-01_00:00:00 MAX AT i,j,k: 278 56
> 21 vert_cfl,w,d(eta)= 2879.670 56544.66 3.2001421E-02
> Timing for main: time 1967-01-01_00:01:30 on domain 1: 13.09157
> elapsed seconds
>
>
> *time step = 30s, namelist.input &domains smooth_cg_topo = .true.*
>
> d01 1967-01-01_00:00:00 5537 points exceeded cfl=2 in domain d01
> at time 1967-01-01_00:00:00 hours
> d01 1967-01-01_00:00:00 MAX AT i,j,k: 283 42
> 2 vert_cfl,w,d(eta)= 2.4396536E+07 NaN 9.9999905E-03
> d01 1967-01-01_00:00:00 1906 points exceeded cfl=2 in domain d01
> at time 1967-01-01_00:00:00 hours
> d01 1967-01-01_00:00:00 MAX AT i,j,k: 21 190
> 20 vert_cfl,w,d(eta)= 1102.228 -6444.851 3.5938144E-02
>
>
>
> *time step = 10s, namelist.input &domains smooth_cg_topo = .true. *
>
> d01 1967-01-01_00:00:00 2548 points exceeded cfl=2 in domain d01
> at time 1967-01-01_00:00:00 hours
> d01 1967-01-01_00:00:00 MAX AT i,j,k: 285 179
> 23 vert_cfl,w,d(eta)= 8.4951393E+14 2.3136813E+23 2.4293438E-02
> d01 1967-01-01_00:00:00 987 points exceeded cfl=2 in domain d01
> at time 1967-01-01_00:00:00 hours
> d01 1967-01-01_00:00:00 MAX AT i,j,k: 285 196
> 14 vert_cfl,w,d(eta)= 24310.53 372558.9 6.8435431E-02
> Timing for main: time 1967-01-01_00:00:10 on domain 1: 15.84628
> elapsed seconds
>
>
> *The namelist.input file: *
>
> &time_control
> run_days = 3,
> run_hours = 0,
> run_minutes = 0,
> run_seconds = 0,
> start_year = 1967,
> start_month = 01,
> start_day = 01,
> start_hour = 00,
> start_minute = 00,
> start_second = 00,
> end_year = 1967,
> end_month = 01,
> end_day = 04,
> end_hour = 00,
> end_minute = 00,
> end_second = 00,
> interval_seconds = 21600
> input_from_file = .true.
> history_interval = 60,
> frames_per_outfile = 1000,
> restart = .false.,
> restart_interval = 5000,
> io_form_history = 2
> io_form_restart = 2
> io_form_input = 2
> io_form_boundary = 2
> debug_level = 0
> /
>
> &domains
> time_step = 10,
> time_step_fract_num = 0,
> time_step_fract_den = 1,
> max_dom = 1,
> s_we = 1,
> s_sn = 1,
> s_vert = 1,
> e_we = 290,
> e_sn = 200,
> e_vert = 30,
> p_top_requested = 5000,
> num_metgrid_levels = 27,
> num_metgrid_soil_levels = 4,
> dx = 30000,
> dy = 30000,
> grid_id = 1,
> parent_id = 1,
> i_parent_start = 1,
> j_parent_start = 1,
> smooth_option = 0
> smooth_cg_topo = .true.
> /
>
> &physics
> mp_physics = 3,
> ra_lw_physics = 1,
> ra_sw_physics = 1,
> radt = 30,
> sf_sfclay_physics = 1,
> sf_surface_physics = 2,
> bl_pbl_physics = 1,
> bldt = 0,
> cu_physics = 1,
> cudt = 5,
> isfflx = 1,
> ifsnow = 1,
> icloud = 1,
> surface_input_source = 1,
> num_soil_layers = 4,
> sf_urban_physics = 0,
> /
>
> &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,
> /
>
> &bdy_control
> spec_bdy_width = 5,
> spec_zone = 1,
> relax_zone = 5,
> specified = .true.,
> nested = .false.,
> /
>
> &grib2
> /
>
> &namelist_quilt
> nio_tasks_per_group = 0,
> nio_groups = 1,
> /
>
>
> Thank you very much,
>
> Yaoping Wang
>
>
> _______________________________________________
> Wrf-users mailing list
> Wrf-users at ucar.edu
> http://mailman.ucar.edu/mailman/listinfo/wrf-users
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/wrf-users/attachments/20160330/b31bf076/attachment.html
More information about the Wrf-users
mailing list