NCAR Mesoscale and Microscale Meteorology Division

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NCL for WRF Model Output
The NCL scripts for plotting WRF model output are
our first cut at producing plots for use in our
development efforts.
The scripts do not constitute and analysis
package.
NCL is an interpreted language allowing for fast
and easy prototyping, built in capabilities to
easily read and write a variety of data formats,
complete NCAR Graphics capabilities, and easy
linking to Fortran and C routines. Thus we may
build an analysis package based on NCL in the
future.
Dont be shy about digging into the scripts!
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Using NCL with WRF Model Output
After downloading WRF-NCL tar file
(wrf_plot_ncl.tar), build the fortran shared
library using the script make_ncl_fortran.
Step 1
Step 2
Place the WRF output file into the ncl directory
with the scripts.
Step 3
Edit one of the scripts for producing the
desired WRF plots, setting the appropriate input
file name And desired output format.
Step 4
Run the script ncl 4
Example WRF NCL Plotting Script
script to produce standard plots for a wrf
real-data run load "wrf_plot.ncl" load
"wrf_user.ncl" load "gsn_code.ncl" load
"skewt_func.ncl" a addfile("wrfout_01_000000.n
c","r") wks wrf_open_X11()
output to screen wks wrf_open_ncgm("wrf_plots")
output to ncgm wks wrf_open_PS("wrf_plots")
output to postscript frame(wks) allow
for window resize before beginning plots times
wrf_user_list_times(a) get times in the
file pressure_levels (/ 850., 700., 500.,
300./) pressure levels to plot ntimes
dimsizes(times) number of times in the
file nlevels dimsizes(pressure_levels)
number of pressure levels
Files containing NCL functions and routines
open netcdf file
output options
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Example WRF NCL Plotting Script (cont.)
Loop through all times in the output file
do it 0, ntimes-1 time it
print(times(it)) if (it.eq.0) then
time_save times(it) end if hours it6.
start with surface pressure plot slvl
wrf_user_getvar(a,"slvl",time) psl
wrf_user_filter2d(slvl, 3) filter the fields
tc wrf_user_getvar(a,"tc",time) tc
1.8tc32. u wrf_user_getvar(a,"ua",time)
ua is u averaged to mass points v
wrf_user_getvar(a,"va",time) va is v averaged
to mass points u u1.94386 v v1.94386
tc_plane tc(0,,) u_plane u(0,,)
v_plane v(0,,)
Function (wrf_user_getvar) that reads data from
the WRF output file and computes appropriate
diagnostic fields (if necessary)
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Example WRF NCL Plotting Script (cont.)
opts_tc True opts_tc_at_MainTitle "Surface
T (F, color) SLP (mb) and winds (kts)" and
many more options... opts_psl True
and many more options... opts_vct True
opts_vct_at_NumVectors 47 opts_vct_at_WindBarbsOn
True opts_vct_at_NoTitles True
opts_vct_at_vcWindBarbColor "black"
opts_vct_at_vcRefAnnoOn False opts_mp True
and many more options... map
wrf_new_map(wks,a,opts_mp) opts_map True
opts_map_at_LabelFont "HELVETICA-BOLD"
opts_map_at_LabelFontHeight .01
wrf_maplabel(wks,map,opts_map)
Options for plots. Logical variable is True if
options are present, options are attributes of
the logical variable
Create map background, label map
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Example WRF NCL Plotting Script (cont.)
Create plots (contour fill/line and vector)
contour_tc wrf_new_fill_contour(wks,tc_p
lane,opts_tc) contour_psl
wrf_new_line_contour(wks,slvl(,),opts_psl)
vector wrf_new_vector(wks,u_plane,
v_plane,opts_vct) wrf_mapoverlay(map,contour_
tc) wrf_mapoverlay(map,contour_psl)
wrf_mapoverlay(map,vector) draw(map)
frame(wks)
Combine individual plots into single picture
(overlay or merge)
Send picture to output device
Clear for the next picture
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Example WRF NCL Plotting Script (cont.)
preparing for 3-D plots p
wrf_user_getvar(a, "p",time) pressure is our
vertical coordinate z wrf_user_getvar(a,
"Z",time) grid point height rh
wrf_user_getvar(a,"rh",time) w
wrf_user_getvar(a,"wa",time) w 100.w tc
(tc-32.).55555 do level 0,nlevels-1
pressure pressure_levels(level) z_plane
wrf_user_intrp3d( z,p,ter,"h",pressure,0.)
tc_plane wrf_user_intrp3d(tc,p,ter,"h",pressure,
0.) u_plane wrf_user_intrp3d(
u,p,ter,"h",pressure,0.) v_plane
wrf_user_intrp3d( v,p,ter,"h",pressure,0.)
rh_plane wrf_user_intrp3d( rh,p,ter,"h",pressur
e,0.) w_plane wrf_user_intrp3d(
w,p,ter,"h",pressure,0.) lots of
plotting... end do
Loop over desired pressure surface for plots
Vertical interp to desired surface
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Example WRF NCL Plotting Script (cont.)
Vertical cross sections
do ip 1, 2 dimsrh dimsizes(rh)
plane new(2,float) plane (/ dimsrh(2)/2,
dimsrh(1)/2 /) if(ip .eq. 1) angle
90. else angle 0. end if
rh_plane wrf_user_intrp3d(rh,z,ter,"v",plane,ang
le) tc_plane wrf_user_intrp3d(tc,z,ter,"v",p
lane,angle) lots of plotting... end do
Point in model gridpoint space
Angle of plane passing through gridpoint
Interpolation to vertical cross section
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Example WRF NCL Plotting Script (cont.)
qv wrf_user_getvar(a,"QVAPOR",time) td
wrf_user_getvar(a,"td",time) u
wrf_user_getvar(a,"umet",time) v
wrf_user_getvar(a,"vmet",time) u u1.94386
v v1.94386 bunch of options locr
wrf_user_find_ij_lat_long(a, 39.77, 104.87 )
loc floattointeger(locr) loc_str "Skew-T at
Denver valid at " times(it) skewt_bkgd
skewT_BackGround (wks, skewtOpts) draw
(skewt_bkgd) skewT_data skewT_PlotData(wks,
skewt_bkgd, p(,loc(0), loc(1)), \
tc(,loc(0),
loc(1)), \
td(,loc(0), loc(1)), \
z(,loc(0), loc(1)),
\
-u(,loc(0), loc(1)), \
-v(,loc(0), loc(1)), \
dataOpts
) frame(wks) end do end do
Skew-T plots First get necessary variables
Find nearest gridpoint
Options needed (skewOpts) not shown here
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NCL for WRF Model Output
The NCL scripts for plotting WRF model output are
our first cut at producing plots for use in our
development efforts.
The scripts do not constitute and analysis
package.
NCL is an interpreted language allowing for fast
and easy prototyping, built in capabilities to
easily read and write a variety of data formats,
complete NCAR Graphics capabilities, and easy
linking to Fortran and C routines. Thus we may
build an analysis package based on NCL in the
future.
Dont be shy about digging into the scripts!