本文详细介绍了如何利用美国1度天气预报数据，通过嵌套域设计实现北京市及其周边区域的精细化天气预报。包括下载特定分辨率的数据文件，设置多级嵌套区域（D01、D02、D03）进行逐级细化分析，以及调整WPS目录下的namelist.wps和WRFV3/test/em_real/namelist.input文件以匹配预报需求。通过NCL工具可视化域设计，最终实现对特定地理区域的高精度天气预报。
我通常是先根据数值天气预报的“分辨率”和要观察的经纬度范围来设计。
1、数值天气预报：
美国数值天气预报提供分辨率为1度、0.5度、1.5度的等等。 欧洲天气预报提供分辨率为0.125度、0.25度的等等。 当然是选择分辨率越小的数值天气预报越好，但这样做下载数据文件会很大。
本例子中采用美国1度的数值天气预报。（在http://motherlode.ucar.edu/native/grid/NCEP/GFS/Global_onedeg/ 中下载，本例子中下载 GFS_Global_onedeg_20110815_0000.grib2 文件）。
2、嵌套域设计（例子中采用降尺度1:3:3）：
假设：北京市的中心经纬度点：116.39，39.92
D03域：取2度的正方形，范围：（117-115，39-41），则需要相当于D01的2格的大小。
D02域：在D03域上下左右各留出2度（相当于D01的2格）。
D01域：在D02域上下左右各留出1度（相当于D01的1格）。
这样：
D01：高和宽为10度，共10个格。
D02：高和宽为 6度，共6*3+1=19个格。
D03：高和宽为 2度，共3*3*2+1=19个格。
3、修改WPS目录下的namelist.wps
&share
wrf_core = 'ARW',
max_dom = 3,
start_date = '2011-08-15_00:00:00','2011-08-15_00:00:00','2011-08-15_00:00:00',
end_date = '2011-08-16_00:00:00','2011-08-16_00:00:00','2011-08-16_00:00:00',
interval_seconds = 10800
io_form_geogrid = 2,
/
&geogrid
parent_id = 1, 1, 2,
parent_grid_ratio = 1, 3, 3,
i_parent_start = 1, 2, 2,
j_parent_start = 1, 2, 2,
e_we = 10, 16, 19,
e_sn = 10, 16, 19,
geog_data_res = '10m','2m', '30s',
dx = 80000,
dy = 80000,
map_proj = 'lambert',
ref_lat = 39.92,
ref_lon = 116.39,
truelat1 = 30.0,
truelat2 = 60.0,
stand_lon = 116.39,
geog_data_path = '/software/geog'
/
&ungrib
out_format = 'WPS',
prefix = 'FILE',
/
&metgrid
fg_name = 'FILE'
io_form_metgrid = 2,
/
4、修改WRFV3/test/em_real/namelist.input
&time_control
run_days = 0,
run_hours = 24,
run_minutes = 0,
run_seconds = 0,
start_year = 2011,2011,2011,
start_month = 08,08,08,
start_day = 15,15,15,
start_hour = 00,00,00,
start_minute = 00,00,00,
start_second = 00,00,00,
end_year = 2011,2011,2011,
end_month = 08,08,08,
end_day = 16,16,16,
end_hour = 00,00,00,
end_minute = 00,00,00,
end_second = 00,00,00,
interval_seconds = 10800
input_from_file = .true.,.true.,.true.,
history_interval = 180, 15, 10,
frames_per_outfile = 1000, 1000, 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 = 180,
time_step_fract_num = 0,
time_step_fract_den = 1,
max_dom = 3,
e_we = 10, 16, 19,
e_sn = 10, 16, 19,
e_vert = 28, 28, 28,
p_top_requested = 5000,
num_metgrid_levels = 27,
num_metgrid_soil_levels = 4,
dx = 80000, 26666.6, 8888.8,
dy = 80000, 26666.6, 8888.8,
grid_id = 1, 2, 3,
parent_id = 0, 1, 2,
i_parent_start = 1, 2, 2,
j_parent_start = 1, 2, 2,
parent_grid_ratio = 1, 3, 3,
parent_time_step_ratio = 1, 3, 3,
feedback = 1,
smooth_option = 0
/
&physics
mp_physics = 3, 3, 3,
ra_lw_physics = 1, 1, 1,
ra_sw_physics = 1, 1, 1,
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,
cu_physics = 1, 1, 1,
cudt = 5, 5, 5,
isfflx = 1,
ifsnow = 0,
icloud = 1,
surface_input_source = 1,
num_soil_layers = 4,
sf_urban_physics = 0, 0, 0,
maxiens = 1,
maxens = 3,
maxens2 = 3,
maxens3 = 16,
ensdim = 144,
/
&fdda
/
&dynamics
w_damping = 0,
diff_opt = 1,
km_opt = 4,
diff_6th_opt = 0, 0, 0,
diff_6th_factor = 0.12, 0.12, 0.12,
base_temp = 290.
damp_opt = 0,
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 = 1, 1, 1,
scalar_adv_opt = 1, 1, 1,
&bdy_control
spec_bdy_width = 5,
spec_zone = 1,
relax_zone = 4,
specified = .true., .false.,.false.,
nested = .false., .true.,.true.,
/
&grib2
/
&namelist_quilt
nio_tasks_per_group = 0,
nio_groups = 1,
/
5、用NCL查看域设计：[也可以可视化地修改域设计]
用ncl工具查看：
执行命令： ncl wrf_wps_show_domain_namelist.ncl
ncl的wrf_wps_show_domain_namelist.ncl 可以在http://www.mmm.ucar.edu/wrf/OnLineTutorial/Graphics/NCL/NCL_examples.htm 下载，只需修改wrf_wps_show_domain_namelist.ncl 文件中的;
#read the following namelist file
filename = "/software/WPS/namelist.wps" #这里输入你的namelist.wps文件路径。
展示图如下：
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