PyNGL example vector plotsΒΆ

Software requirements:

  • Python 2.7.x

  • Numpy 1.9.2

  • PyNGL/PyNIO 1.5.0

Run the vector example script:

python PyNGL_vector_rectilinear.py

Script PyNGL_vector_rectilinear.py:

'''
 DKRZ PyNGL Script: PyNGL_vector_rectilinear.py

 Description:       Python script using PyNGL Python module
                    - vector plot on map (rectilinear data)
                      1st plot :  vectors on global map, colored
                      2nd plot :  vectors colored by temperature
                       - curly vectors

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

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

    #--  define variables
    diri   = "$HOME/NCL/general/data/new_data/" #-- data directory
    fname  = "rectilinear_grid_2D.nc"           #-- data file name

    minval =  250.                              #-- minimum contour level
    maxval =  315                               #-- maximum contour level
    inc    =    5.                              #-- contour level spacing

    #--  open file and read variables
    f      = Nio.open_file(diri + fname,"r")    #-- open data file
    temp   = f.variables["tsurf"][0,::-1,:]     #-- first time step, reverse latitude
    u      = f.variables["u10"][0,::-1,:]       #-- first time step, reverse latitude
    v      = f.variables["v10"][0,::-1,:]       #-- first time step, reverse latitude
    lat    = f.variables["lat"][::-1]           #-- reverse latitudes
    lon    = f.variables["lon"][:]              #-- all longitudes

    nlon   = len(lon)                           #-- number of longitudes
    nlat   = len(lat)                           #-- number of latitudes

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

    #-- create 1st plot: vectors on global map
    res                           =  Ngl.Resources()
    res.vfXCStartV                =  float(lon[0])                #-- minimum longitude
    res.vfXCEndV                  =  float(lon[len(lon[:])-1])    #-- maximum longitude
    res.vfYCStartV                =  float(lat[0])                #-- minimum latitude
    res.vfYCEndV                  =  float(lat[len(lat[:])-1])    #-- maximum latitude

    res.tiMainString              = "~F25~Wind velocity vectors"  #-- title string
    res.tiMainFontHeightF         =  0.024                        #-- decrease title font size

    res.mpLimitMode               = "Corners"                     #-- select a sub-region
    res.mpLeftCornerLonF          =  float(lon[0])                #-- left longitude value
    res.mpRightCornerLonF         =  float(lon[len(lon[:])-1])    #-- right longitude value
    res.mpLeftCornerLatF          =  float(lat[0])                #-- left latitude value
    res.mpRightCornerLatF         =  float(lat[len(lat[:])-1])    #-- right latitude value

    res.mpPerimOn                 =  True                         #-- turn on map perimeter

    res.vpXF                      =  0.1                          #-- viewport x-position
    res.vpYF                      =  0.92                         #-- viewport y-position
    res.vpWidthF                  =  0.75                         #-- viewport width
    res.vpHeightF                 =  0.75                         #-- viewport height

    res.vcMonoLineArrowColor      =  False                        #-- draw vectors in color
    res.vcMinFracLengthF          =   0.33                        #-- increase length of vectors
    res.vcMinMagnitudeF           =   0.001                       #-- increase length of vectors
    res.vcRefLengthF              =   0.045                       #-- set reference vector length
    res.vcRefMagnitudeF           =  20.0                         #-- set reference magnitude value
    res.vcLineArrowThicknessF     =   6.0                         #-- make vector lines thicker (default: 1.0)

    res.pmLabelBarDisplayMode     = "Always"                      #-- turn on a labelbar
    res.lbOrientation             = "Horizontal"                  #-- labelbar orientation
    res.lbLabelFontHeightF        =  0.008                        #-- labelbar label font size
    res.lbBoxMinorExtentF         =  0.22                         #-- decrease height of labelbar boxes

    #-- draw first plot
    map1 = Ngl.vector_map(wks,u[::3,::3],v[::3,::3],res)           #-- draw a vector plot

    #-- create 2nd plot: sub-region colored by temperature variable
    tempa = (temp-273.15)*9.0/5.0+32.0                            #-- convert from Kelvin to Fahrenheit

    res.mpLimitMode               = "LatLon"                      #-- change the area of the map
    res.mpMinLatF                 =  18.0                         #-- minimum latitude
    res.mpMaxLatF                 =  65.0                         #-- maximum latitude
    res.mpMinLonF                 = -128.                         #-- minimum longitude
    res.mpMaxLonF                 = -58.                          #-- minimum longitude

    res.mpFillOn                  =  True                         #-- turn on map fill
    res.mpLandFillColor           =  16                           #-- change land color to grey
    res.mpOceanFillColor          =  -1                           #-- change color for oceans and inlandwater
    res.mpInlandWaterFillColor    =  -1                           #-- set ocean/inlandwater color to transparent
    res.mpGridMaskMode            = "MaskNotOcean"                #-- draw grid over ocean, not land
    res.mpGridLineDashPattern     =   2                           #-- grid dash pattern
    res.mpOutlineBoundarySets     = "GeophysicalAndUSStates"      #-- outline US States

    res.vcFillArrowsOn            =  True                         #-- fill the vector arrows
    res.vcMonoFillArrowFillColor  =  False                        #-- draw vectors with colors
    res.vcFillArrowEdgeColor      =  1                            #-- draw the edges in black
    res.vcGlyphStyle              = "CurlyVector"                 #-- draw nice curly vectors
    res.vcLineArrowThicknessF     =   5.0                         #-- make vector lines thicker (default: 1.0)

    res.tiMainString              = "~F25~Wind velocity vectors"  #-- title string

    res.lbTitleString             = "TEMPERATURE (~S~o~N~F)"      #-- labelbar title string
    res.lbTitleFontHeightF        =  0.010                        #-- labelbar title font size
    res.lbBoxMinorExtentF         =  0.18                         #-- decrease height of labelbar boxes

    #-- draw 2nd plot
    map2 = Ngl.vector_scalar_map(wks,u[::1,::1],v[::1,::1],tempa[::1,::1],res)

    #-- done
    Ngl.end()

if __name__ == '__main__':
    main()

Result:

PyNGL rectilinear vector 1 w400

PyNGL rectilinear vector 2 w400