Rotating map plot using basemap in python

Question

I am trying to plot data from a netcdf using Basemap but I guess since the latitude indices are inverted I get a map that is upside down. How should I fix this? Thanks!

fnc = Dataset(ncfile, 'r')
lat = fnc.variables['latitude'][:]
lon = fnc.variables['longitude'][:]
level = fnc.variables['level']
mydata = fnc.variables['Data'][:]
imgplot = plt.imshow(mydata[0, 0, :, :])
imgplot.set_cmap('RdYlGn')
plt.colorbar()
plt.show

m = Basemap(llcrnrlon = -180, llcrnrlat = -90, urcrnrlon = 180, urcrnrlat= +90, resolution = 'l', epsg=4326)
x, y = m(lon, lat)
im = m.imshow(mydata[0, 0, :, :])
m.drawcoastlines()
plt.show()

N1B4 · Accepted Answer · 2016-07-12 17:52:17Z

1

First, note that you're currently reading in one dimension of Data:

mydata = fnc.variables['Data'][:]

but later you're trying to extract slices of it as if it were 4D:

imgplot = plt.imshow(mydata[0, 0, :, :])

So, you'll want to read-in all 4 dimensions of Data (perhaps those are time, level, lat, lon?):

mydata = fnc.variables['Data'][:,:,:,:]

and then reverse latitudes using the ::-1 syntax:

imgplot.plotimshow(mydata[0, 0, ::-1, :])

answered Jul 12, 2016 at 17:52

N1B4

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1 Comment

user26750 Over a year ago

Thanks for the quick reply. I have a follow up question as well and would appreciate it if you could help me there as well stackoverflow.com/questions/38338177/…

kakk11 · Accepted Answer · 2016-07-12 17:54:15Z

0

I believe that plotting command needs to be aware of the map coordinates x,y. Try to replace the

im = m.imshow(mydata[0, 0, :, :])

with

m.pcolormesh(x,y,mydata[0,0,:,:])

and it should work.

answered Jul 12, 2016 at 17:54

kakk11

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