Stream: python-questions

Topic: Simple sea ice plot

view this post on Zulip David Bailey (Sep 24 2021 at 18:49):

I am just trying to do a contourf NH projection of sea ice concentration. I am just trying to use matplotlib and keep it simple. This is an example for a reporter to see for using the CESM1-LENS data. I am not getting anything on my plot and I am confused about needing meshgrid or not. The code is very straightforward. Anyone have some thoughts on it?

Python northern hemisphere plot

import os
import numpy as np
import xarray as xr
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt

dset = xr.open_dataset('icefracLE-09-2080.nc')

icefrac = dset['ICEFRAC'][0,:,:]
lat = dset['lat'][:]
lon = dset['lon'][:]

lons, lats = np.meshgrid(lon, lat)

create Basemap instance.

map = Basemap(projection='npstere',lon_0=0,lat_0=90,boundinglat=50,resolution='l')

x,y = map(lons,lats)

cs = map.contourf(x,y,icefrac,30,cmap=plt.cm.jet)
plt.show()

view this post on Zulip Max Grover (Sep 24 2021 at 19:22):

I was able to run this on the JupyterHub running the following

import os
import numpy as np
import xarray as xr
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt

dset = xr.open_dataset('/glade/campaign/cesm/collections/cesmLE/CESM-CAM5-BGC-LE/atm/proc/tseries/monthly/ICEFRAC/b.e11.B20TRLENS_RCP85.f09_g16.xghg.003.cam.h0.ICEFRAC.200601-208012.nc')

icefrac = dset['ICEFRAC'][0,:,:]
lat = dset['lat'][:]
lon = dset['lon'][:]

lons, lats = np.meshgrid(lon, lat)

#create Basemap instance.
map = Basemap(projection='npstere',lon_0=0,lat_0=90,boundinglat=50,resolution='l')

x,y = map(lons,lats)

cs = map.contourf(x,y,icefrac,30,cmap=plt.cm.jet)

plt.show()

Are you running this from a script? If so, you may want to save out the png (plt.savefig('fig_title.png' screenshot_ice_image.png )

view this post on Zulip David Bailey (Sep 24 2021 at 19:35):

Interesting. I am running this from a script. Here is what I get. icefrac.png Note that when I try to run this with python3 I get the following error. So, I switch to python2.7.9 and it runs, but just not the right thing.

(NPL) [dbailey@cheyenne6 ~/for_kati]> python ice_north.py
Traceback (most recent call last):
File "ice_north.py", line 6, in <module>
from mpl_toolkits.basemap import Basemap
File "/glade/u/apps/ch/opt/python/3.7.9/gnu/9.1.0/pkg-library/20201220/lib/python3.7/site-packages/mpl_toolkits/basemap/__init__.py", line 50, in <module>
from .proj import Proj
File "/glade/u/apps/ch/opt/python/3.7.9/gnu/9.1.0/pkg-library/20201220/lib/python3.7/site-packages/mpl_toolkits/basemap/proj.py", line 6, in <module>
from matplotlib.cbook import dedent
ImportError: cannot import name 'dedent' from 'matplotlib.cbook' (/glade/u/apps/ch/opt/python/3.7.9/gnu/9.1.0/pkg-library/20201220/lib/python3.7/site-packages/matplotlib/cbook/__init__.py)

view this post on Zulip David Bailey (Sep 24 2021 at 19:36):

I am also using the ncar_pylib environment on casper.

view this post on Zulip Max Grover (Sep 24 2021 at 19:52):

@David Bailey could you point me to the path of the data file you are using?

view this post on Zulip David Bailey (Sep 24 2021 at 19:52):

Sure. /glade/u/home/dbailey/for_kati/ice_north.py

Dave

view this post on Zulip David Bailey (Sep 24 2021 at 19:57):

Haha. Nevermind. I was looking at 2080 in the RCP8.5 and there is no ice left in the NH in September.

view this post on Zulip Max Grover (Sep 24 2021 at 19:59):

Yeah - that's what I was about to respond with... there is on small area with ~0.04 (4%), but that's it Screen-Shot-2021-09-24-at-1.59.37-PM.png

view this post on Zulip David Bailey (Sep 24 2021 at 20:55):

Got it worked out now and getting the plot I was expecting. icefrac.png

Last updated: Jan 30 2022 at 12:01 UTC