Data files for some examples
Example pages containing:
Lambert Conformal Projection
This suite of examples uses an older and deprecated method of
plotting WRF data. We recommend that you visit the more up-to-date
for examples of using NCL to plot WRF-ARW data.
The WRF variables on the 'real data' netCDF file used in the examples
are on a native Lambert Conformal
projection. By default, when data are placed onto a map, NCL performs
a transformation to the specified projection. This transformation is
not needed for native grids. To turn off this default behavior, set
tfDoNDCOverlay = True. This will
result in faster graphic generation.
The gsm_csm_*map* suite of interfaces expect global data. If plotting
regionl data, it is necessary to set gsnAddCyclic = False
The WRF netCDF file contains the information needed to properly plot
the grid, specifically: (i) the global attributes TRUELAT1, TRUELAT2
and CEN_LON and (ii) the grid latitudes (XLAT) and longitudes
(XLONG). The required approach to plotting the data upon a native
projection is to specify mpLimitMode = "Corners".
: Basic black and white
contour on Lambert Conformal Map. This example explicitly sets all the
resources for correctly contouring the data upon a
native Lambert Conformal
Because the spatial coordinate variables XLAT, XLONG and ZNU do not
change with time, only values from the initial time are read.
: A color version.
cnFillOn = True, turns on color
contours while gsn_define_colormap
allows the user to change the color map. This can be from a set of
tables or various other
techniques such as specifying named colors or RGB triplets.
pmTickMarkDisplayMode = "Always"
turns on the map tickmarks. The top and right side lat/lon labels may
be turned off by setting tmXTOn =
False and tmYROn = False.
Each native Lambert Conformal Projection plot must specify the same
set of map resources. This example, and all subsequent examples on
this page, hide these resources in "WRF_map_c" in
: A panel plot.
gsn_panel is the procedure that
controls the placement of multiple plots on a page. It expects a
different resource variable (e.g. res vs. panel_res) since there are
several panel-only options. The panel
example page demonstrates these options.
: Panel a specified
variable. Plot forecast every 6 hours. When panelling an individual
variable, it is desirable to have one common label bar.
nice_mnmxintvl can be used to determine "nice"
: The WRF netCDF file does
not have a missing value attribute (e.g. _FillValue). The SMOIS
(soil moisture) and SST (sea surface temperature) variables use 1.0
and 0.0, respectively, to indicate out of range or missing values.
These were determined by examining the file. The _FillValue for each
variable must be set manually.
The orientation of the label bar can be changed from the default
horizontal by setting lbOrientation
cnFillMode = "RasterFill", turns
on color rasters.
: Use the RAINC and
RAINNC variables to calculate the total precipitation. Prior
to calculating the total, the
algebraic operator ">" is used to ensure that negative values
are set to zero.
named colors are
used create a custom color map. Each color matches the unequally
spaced contour levels specified by the user.
:Basic vectors and wind
The U and V components are on a staggered grid. Array syntax is used to
create u and v on the mass grid whose grid locations are specified by
XLAT and XLONG.
u = 0.5*(U(nt,kl,:,0:mlonU-2)+U(nt,kl,:,1:mlonU-1))
v = 0.5*(V(nt,kl,0:nlatV-2,:)+V(nt,kl,1:nlatV-1,:))
: Overlay winds at 10
meters (U10, V10) over the total precipitation. Meteorological wind
barbs are used to indicate direction and speed.
gsnMaximize is used to maximize the
Cross sections along user specified latitudes
and longitudes of the Lambert Conformal grid.
The eta [ZNU] vertical coordinate is scaled such
that it simulates pressure levels.
This allows gsn_csm_pres_hgt
to be used.