PyNGL example curvilinear contour plot

Software requirements:

• Python 3

• PyNGL 1.6.1

• xarray

Run the curvilinear contour example script:

python PyNGL_curvilinear_contour.py

Script PyNGL_curvilinear_contour.py:

"""
DKRZ PyNGL Script: PyNGL_curvilinear_contour.py

Description: Python script using PyNGL Python module
  - plot curvilinear data

Grid type: Curvilinear grid

Settings: - colormap,
  - draw edges

09.02.21 meier-fleischer(at)dkrz.de
"""
import xarray as xr
import Ngl

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

    #-- define variables
    diri = '/sw/spack-levante/ncl-6.6.2-r3hsef/lib/ncarg/data/nug/' #-- data directory
    fname = 'tos_ocean_bipolar_grid.nc' #-- curvilinear data

    #-- open file and read variables
    ds = xr.open_dataset(diri + fname)

    tos = ds.tos[0,:,:]
    lat2d = ds.lat[:,:]
    lon2d = ds.lon[:,:]

    var = tos.to_masked_array() #-- use variable _FillValues to mask data

    #-- open a workstation
    wkres = Ngl.Resources() #-- generate an resources object for workstation
    wkres.wkWidth = 1024 #-- width of workstation
    wkres.wkHeight = 1024 #-- height of workstation
    wks_type = 'png' #-- output type

    wks = Ngl.open_wks(wks_type,"Py_curvilinear_contour",wkres)

    #-- set resources
    res = Ngl.Resources() #-- generate an resources object for plot

    #-- viewport resources
    res.vpWidthF = 0.94 #-- width of viewport
    res.vpHeightF = 0.9 #-- height of viewport

    #-- contour resources
    res.cnFillOn = True #-- turn on contour fill
    res.cnLinesOn = False #-- don't draw contour lines
    res.cnLineLabelsOn = False #-- don't draw line labels
    res.cnFillPalette = 'BlueWhiteOrangeRed'
    res.cnFillMode = 'CellFill' #-- change contour fill mode
    res.cnCellFillEdgeColor = 'black' #-- edges color
    res.cnCellFillMissingValEdgeColor = 'gray50' #-- missing value edges color
    res.cnMissingValFillColor = 'gray50' #-- missing value fill color

    #-- labelbar resources
    res.lbOrientation = 'Horizontal' #-- labelbar orientation

    res.tiMainString = 'Curvilinear grid: MPI-ESM-LR (2D lat/lon arrays)'
    res.tiMainFontHeightF = 0.022 #-- main title font size

    #-- grid data to be used
    res.sfXArray = lon2d.values #-- longitude grid cell center
    res.sfYArray = lat2d.values #-- latitude grid cell center

    #-- map resources
    res.mpFillOn = False #-- don't draw filled map
    res.mpGridLatSpacingF = 10. #-- grid lat spacing
    res.mpGridLonSpacingF = 10. #-- grid lon spacing
    res.mpDataBaseVersion = 'MediumRes' #-- map database
    res.mpLimitMode = 'LatLon' #-- must be set using minLatF/maxLatF/minLonF/maxLonF
    res.mpMinLatF = -10. #-- sub-region minimum latitude
    res.mpMaxLatF = 80. #-- sub-region maximum latitude
    res.mpMinLonF = -120. #-- sub-region minimum longitude
    res.mpMaxLonF = 60. #-- sub-region maximum longitude

    #-- create the plot
    plot = Ngl.contour_map(wks, var, res) #-- create the contour plot

    #-- done
    Ngl.end()

 if __name__ == '__main__':
     main()

Plot result: