On Mon, Oct 3, 2011 at 6:51 PM, questions anon <questions.a...@gmail.com>wrote:
> Hi All,
> Is there a simple way to plot a directional arrow to represent a degree?
> I have a netcdf file containing wind direction as degrees and I would like
> to make a plot with all little arrows representing the wind direction.
> Below is the code I am using currently to plot wind direction but am not
> sure where/how to add directional arrows.
> Thanks
>
>
> from netCDF4 import Dataset
> import numpy as N
> import pylab as plt
> from numpy import ma as MA
> from mpl_toolkits.basemap import Basemap
> import os
>
> ncfile=Dataset('E:/WINDDIR/IDZ00026_VIC_ADFD_Wind_Dir_SFC.nc', 'r+',
> 'NETCDF4')
> WDIR=ncfile.variables['Wind_Dir_SFC'][-50]
> LAT=ncfile.variables['latitude'][:]
> LON=ncfile.variables['longitude'][:]
> TIME=ncfile.variables['time'][-50]
> fillvalue=ncfile.variables['Wind_Dir_SFC']._FillValue
> WDIR=MA.masked_values(WDIR, fillvalue)
> ncfile.close()
>
> map = Basemap(projection='merc',llcrnrlat=-40,urcrnrlat=-33,
> llcrnrlon=139.0,urcrnrlon=151.0,lat_ts=0,resolution='i')
> x,y=map(*N.meshgrid(LON,LAT))
> map.drawstates()
> map.drawcoastlines()
> plt.title('Wind Direction')
> CS = map.contourf(x,y,WDIR,15, cmap=plt.cm.jet)
> l,b,w,h =0.1,0.1,0.8,0.8
> cax = plt.axes([l+w+0.025, b, 0.025, h])
> plt.colorbar(CS,cax=cax,drawedges=True)
> plt.savefig((os.path.join('E:/WINDDIR/', 'WDIRSFC.png')))
> plt.show()
>
>
Would the barb() command do what you want?
http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.barbs
http://matplotlib.sourceforge.net/examples/pylab_examples/barb_demo.html
They aren't arrows, but they are commonly used in meteorology to plot
windfields.
Cheers,
Ben Root
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