PyNGL example rectilinear slice plotΒΆ

Software requirements:

  • Python 2.7.x

  • Numpy 1.9.2

  • PyNGL/PyNIO 1.5.0

Run the rectilinear slice contour example script:

python PyNGL_rectilinear_slice.py

Script PyNGL_rectilinear_slice.py:

'''
 DKRZ PyNGL Script: PyNGL_rectilinear_slice.py

 Description:       Python script using PyNGL Python module
                    - slice plot at lat index=69 (rectilinear data)

 2015-06-04  meier-fleischer(at)dkrz.de
'''
import numpy,sys,os
import Ngl,Nio

#-----------------------------------------------------------------------
#-- Function: main
#-----------------------------------------------------------------------
def main():

    #--  define variables
    diri   = "./"                                  #-- data directory
    fname  = "rectilinear_grid_3D.nc"              #-- data file name

    #--  open file and read variables
    f      =  Nio.open_file(diri + fname,"r")      #-- open data file
    t      =  f.variables["t"][0,:,::-1,:]         #-- first time step, reverse latitude
    t70    =  t[:,69,:]                            #-- variable at lat index 69
    lev    =  f.variables["lev"][:]                #-- all levels
    lat    =  f.variables["lat"][::-1]             #-- reverse latitudes
    lon    =  f.variables["lon"][:]                #-- all longitudes
    nlat   =  len(lat)                             #-- number of latitudes

    strlat70 = lat[69]                             #-- retrieve data of lat array index 69

    #-- get the minimum and maximum of the data
    minval =  int(numpy.amin(t))                   #-- minimum value
    maxval =  int(numpy.amax(t))                   #-- maximum value
    inc    =  5                                    #-- contour level spacing
    ncn    =  (maxval-minval)/inc + 1              #-- number of contour levels

    #-- open a workstation
    wkres                     =  Ngl.Resources()   #-- generate an res object for workstation
    wkres.wkWidth             =  1024              #-- plot resolution 2500 pixel width
    wkres.wkHeight            =  1024              #-- plot resolution 2500 pixel height
    wks_type                  = "png"              #-- output type
    wks                       =  Ngl.open_wks(wks_type,"Py_rectilinear_slice",wkres)  #-- open workstation

    #-- set resources
    res                       =  Ngl.Resources()   #-- generate an res object for plot
    res.tiMainString =  f.variables["t"].long_name + " at lat " + "{:.2f}".format(strlat70) + " degrees"
                                                   #-- set main title
    #-- viewport resources
    res.vpXF                  =  0.1               #-- start x-position of viewport
    res.vpYF                  =  0.9               #-- start y-position of viewport
    res.vpWidthF              =  0.7               #-- width of viewport
    res.vpHeightF             =  0.7               #-- height of viewport

    #-- contour resources
    res.cnFillOn              =  True              #-- turn on contour fill
    res.cnLineLabelsOn        =  False             #-- turn off line labels
    res.cnInfoLabelOn         =  False             #-- turn off info label
    res.cnLevelSelectionMode  = "ManualLevels"     #-- select manual levels
    res.cnMinLevelValF        =  minval            #-- minimum contour value
    res.cnMaxLevelValF        =  maxval            #-- maximum contour value
    res.cnLevelSpacingF       =  inc               #-- contour increment

    #-- grid resources
    res.sfXArray              =  lon               #-- scalar field x
    res.sfYArray              =  lev               #-- scalar field y

    #-- labelbar resources
    res.pmLabelBarDisplayMode = "Always"           #-- turn off the label bar

    #-- draw slice contour plot
    plot = Ngl.contour(wks,t70,res)

    #-- done
    Ngl.end()

if __name__ == '__main__':
    main()

Result:

PyNGL rectilinear slice w400