[Wrf-users] Using diff_opt=2 in complex terrain
David Smart
david.smrt at gmail.com
Mon Sep 13 13:08:00 MDT 2010
Dan,
We had problems with CFL violations on a N Atlantic domain (delta x~15km),
apparently due to excessive vertical velocities along the east Greenland
coast. Switching to the Adaptive timestep has helped considerably,
especially with the the Target CFL set to 1. You may have to experiment with
the initial time step and other settings. This is with a PBL scheme.
On a nested 1km grid some, ATM experimental, results suggest that having 3D
diffusion improves the representation of convection and cuts down on
spurious , grid point ppn. 2D diffusion and a PBL are used on the coarser
parent grid(s). With the adaptive timestep this works fine, though the
terrain is rather 'smooth' (southern UK). Have n't tried this yet with
steeper, higher terrain.
I would experiment with the spacing of your lowest levels as well. WRF3.1
Best,
David
On Sat, Sep 11, 2010 at 11:54 PM, Daniel Steinhoff <
steinhoff.9 at buckeyemail.osu.edu> wrote:
> Dear wrf-users,
>
> I am running simulations over the McMurdo Dry Valleys in Antarctica, a
> region of complex terrain (mountain peaks approaching 4000 m, deep valleys,
> coastal). In order to properly simulate cold pools and other features in
> the valleys, I'd like to treat diffusion truly horizontally, as Zangl (2002)
> did in Alpine simulations with MM5. I've seen in the model documentation
> and tutorial presentation that diff_opt=2 should only be used with grid
> spacing < 2 km and without PBL parameterization. Running a 32-8-2 km, 40
> vertical levels nested simulation, I'd like to keep the PBL scheme. Has
> anyone had success using diff_opt=2 for real data cases with a PBL scheme?
>
> When I try diff_opt=2, with km_opt=2, 3, or 4, the simulations are more
> sensitive than otherwise to CFL violations or NaN errors at points on steep
> slopes (this is after extensive terrain smoothing of a 200 m terrain
> dataset). km_opt=2 runs the longest before crashing (about a half hour),
> whereas the other options crash within minutes. Interestingly, these CFL
> violations and NaN errors are more prevalent in the outer grids (for
> example, either the 32 km or 8 km grids along steep slopes). Might I be
> better off running the 32 km and 8 km outer grids with diff_opt=1, and then
> using ndown for an inner grid of 2 km and using diff_opt=2? Or is an
> extremely short timestep required? I've been down to 60 sec on the 32 km
> grid. I have similar problems to above with a 27-9-3-1 km nested grid, 51
> vertical levels (default spacing) setup also.
>
> If anyone has any ideas or advice I'd appreciate it. I am running WRF
> 3.2.1 on NCAR bluefire. I've pasted the namelist below from the 32-8-2 km
> simulations.
>
> Dan
>
>
> &time_control
> run_days = 0,
> run_hours = 60,
> run_minutes = 0,
> run_seconds = 0,
> start_year = 2006, 2006, 2006,
> start_month = 04, 04, 04,
> start_day = 15, 15, 15,
> start_hour = 12, 12, 12,
> start_minute = 00, 00, 00,
> start_second = 00, 00, 00,
> end_year = 2006, 2006, 2006,
> end_month = 04, 04, 04,
> end_day = 18, 18, 18,
> end_hour = 00, 00, 00,
> end_minute = 00, 00, 00,
> end_second = 00, 00, 00,
> interval_seconds = 21600,
> input_from_file = .true.,.true.,.true.,
> history_interval = 360, 360, 360,
> frames_per_outfile = 1, 1, 1,
> restart = .False.,
> restart_interval = 720,
> reset_simulation_start = .false.,
> auxinput4_inname = "wrflowinp_d<domain>",
> auxinput4_interval = 360, 360, 360,
> io_form_history = 2,
> auxinput4_interval = 360, 360, 360,
> io_form_history = 2,
> io_form_restart = 2,
> io_form_input = 2,
> io_form_boundary = 2,
> io_form_auxinput4 = 2,
> nocolons = .false.,
> debug_level = 0,
> auxhist2_outname = "surface_d<domain>_<date>",
> auxhist2_interval = 0, 0, 60,
> io_form_auxhist2 = 2,
> /
>
> &domains
> time_step = 120,
> time_step_fract_num = 0,
> time_step_fract_den = 1,
> max_dom = 3,
> e_we = 200, 161, 193,
> e_sn = 200, 121, 165,
> s_vert = 1, 1, 1,
> e_vert = 40, 40, 40,
> dx = 32000, 8000, 2000,
> dy = 32000, 8000, 2000,
> grid_id = 1, 2, 3,
> parent_id = 0, 1, 2,
> i_parent_start = 1, 68, 54,
> parent_id = 0, 1, 2,
> i_parent_start = 1, 68, 54,
> j_parent_start = 1, 105, 42,
> parent_grid_ratio = 1, 4, 4,
> parent_time_step_ratio = 1, 4, 4,
> feedback = 0,
> smooth_option = 0,
> num_metgrid_levels = 38,
> num_metgrid_soil_levels = 4,
> eta_levels = 1.00000 , 0.99629 , 0.99258 ,
> 0.98767 , 0.98275 ,
> 0.97636 , 0.96996 , 0.96184 , 0.95372
> , 0.93357 ,
> 0.90913 , 0.87957 , 0.84531 , 0.80683
> , 0.76467 ,
> 0.71940 , 0.67163 , 0.62198 , 0.57108
> , 0.51956 ,
> 0.46803 , 0.42030 , 0.37613 , 0.33532
> , 0.29764 ,
> 0.26290 , 0.23092 , 0.20152 , 0.17452
> , 0.14978 ,
> 0.12714 , 0.10646 , 0.08761 , 0.07045
> , 0.05466 ,
> 0.03981 , 0.02580 , 0.01677 , 0.00903
> , 0.00000 ,
> p_top_requested = 5000,
> interp_type = 2,
> extrap_type = 2,
> t_extrap_type = 2,
> use_levels_below_ground = .true.,
> use_surface = .true.,
> lagrange_order = 1,
> lowest_lev_from_sfc = .false.,
> smooth_cg_topo = .false.,
> force_sfc_in_vinterp = 1,
> smooth_cg_topo = .false.,
> force_sfc_in_vinterp = 1,
> zap_close_levels = 0.,
> sfcp_to_sfcp = .false.,
> use_adaptive_time_step = .false.,
> /
>
> &dfi_control
> /
>
> &physics
> mp_physics = 6, 6, 6,
> mp_zero_out = 0,
> no_mp_heating = 0,
> ra_lw_physics = 1, 1, 1,
> ra_sw_physics = 1, 1, 1,
> radt = 30, 10, 10,
> levsiz = 59,
> paerlev = 29,
> cam_abs_dim1 = 4,
> cam_abs_dim2 = 35,
> sf_sfclay_physics = 5, 5, 5,
> sf_surface_physics = 2, 2, 2,
> sf_urban_physics = 0, 0, 0,
> bl_pbl_physics = 5, 5, 5,
> bldt = 0, 0, 0,
> grav_settling = 1, 1, 1,
> bldt = 0, 0, 0,
> grav_settling = 1, 1, 1,
> cu_physics = 3, 0, 0,
> cudt = 5,
> cugd_avedx = 1,
> isfflx = 1,
> ifsnow = 0,
> icloud = 1,
> swrad_scat = 1.,
> surface_input_source = 1,
> num_soil_layers = 4,
> num_land_cat = 24,
> num_soil_cat = 16,
> usemonalb = .false.,
> rdmaxalb = .false.,
> rdlai2d = .false.,
> sst_update = 1,
> seaice_threshold = 0.0,
> tmn_update = 0,
> bucket_mm = -1.,
> maxiens = 1,
> maxens = 3,
> maxens2 = 3,
> maxens3 = 16,
> ensdim = 144,
> slope_rad = 1,
> topo_shading = 1,
> slope_rad = 1,
> topo_shading = 1,
> shadlen = 25000.,
> omlcall = 0,
> oml_hml0 = 50.,
> oml_gamma = 0.14,
> isftcflx = 0,
> fractional_seaice = 1,
> seaice_thickness = 1,
> tice2tsk_if2cold = .true.
> /
>
> &fdda
> grid_fdda = 1, 0, 0,
> gfdda_inname = "wrffdda_d<domain>",
> gfdda_interval_m = 360, 0, 0,
> gfdda_end_h = 60, 0, 0,
> io_form_gfdda = 2,
> fgdt = 0,
> if_no_pbl_nudging_uv = 0, 0, 0,
> if_no_pbl_nudging_t = 0, 0, 0,
> if_no_pbl_nudging_q = 0, 0, 0,
> if_zfac_uv = 1, 0, 0,
> k_zfac_uv = 13,
> if_zfac_t = 1, 0, 0,
> k_zfac_t = 13,
> if_zfac_q = 1, 0, 0,
> k_zfac_t = 13,
> if_zfac_q = 1, 0, 0,
> k_zfac_q = 40,
> guv = 0.0003,0.0000,0.0000,
> gt = 0.0003,0.0000,0.0000,
> gq = 0.0000,0.0000,0.0000,
> if_ramping = 0,
> dtramp_min = 60.0,
> grid_sfdda = 0, 0, 0,
> rinblw = 250.0,
> obs_nudge_opt = 0, 0, 0,
> /
>
> &scm
> /
>
> &dynamics
> rk_ord = 3,
> diff_opt = 2,
> km_opt = 2,
> diff_6th_opt = 1, 1, 1,
> diff_6th_factor = 0.06, 0.06, 0.06,
> damp_opt = 3,
> zdamp = 5000., 5000., 5000.,
> dampcoef = 0.03, 0.03, 0.03,
> w_damping = 0,
> base_temp = 268.,
> w_damping = 0,
> base_temp = 268.,
> base_pres = 100000.,
> base_lapse = 50.,
> khdif = 0, 0, 0,
> kvdif = 0, 0, 0,
> smdiv = 0.1, 0.1, 0.1,
> emdiv = 0.01, 0.01, 0.01,
> epssm = 0.1, 0.1, 0.1,
> non_hydrostatic = .true., .true., .true.,
> h_mom_adv_order = 5, 5, 5,
> v_mom_adv_order = 3, 3, 3,
> h_sca_adv_order = 5, 5, 5,
> v_sca_adv_order = 3, 3, 3,
> time_step_sound = 4, 4, 4,
> moist_adv_opt = 1, 1, 1,
> scalar_adv_opt = 1, 1, 1,
> tke_adv_opt = 1, 1, 1,
> gwd_opt = 0,
> /
>
> &bdy_control
> spec_bdy_width = 5,
> spec_zone = 1,
> relax_zone = 4,
> specified = .true., .false.,.false.,
> spec_exp = 0.,
> specified = .true., .false.,.false.,
> spec_exp = 0.,
> periodic_x = .false.,.false.,.false.,
> symmetric_xs = .false.,.false.,.false.,
> symmetric_xe = .false.,.false.,.false.,
> open_xs = .false.,.false.,.false.,
> open_xe = .false.,.false.,.false.,
> periodic_y = .false.,.false.,.false.,
> symmetric_ys = .false.,.false.,.false.,
> symmetric_ye = .false.,.false.,.false.,
> open_ys = .false.,.false.,.false.,
> open_ye = .false.,.false.,.false.,
> nested = .false.,.true.,.true.,
> /
>
> &grib2
> /
>
> &tc
> /
>
> &fire
> /
>
> &namelist_quilt
> nio_tasks_per_group = 0,
> nio_groups = 1,
>
> 201,2 99%
> nio_tasks_per_group = 0,
> nio_groups = 1,
> /
>
>
> Daniel Steinhoff
> Polar Meteorology Group
> Byrd Polar Research Center
> The Ohio State University
> steinhoff.9 at buckeyemail.osu.edu
>
>
>
>
>
> _______________________________________________
> Wrf-users mailing list
> Wrf-users at ucar.edu
> http://mailman.ucar.edu/mailman/listinfo/wrf-users
>
--
______________________________________
David Smart
Research Associate,
Mesoscale Modelling Facility,
Room G38,
AON Benfield Hazards Research Centre,
University College London,
____________________________________
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