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

# read in data.
file = open('fcover.dat','r')
ul=[];vl=[];pl=[]
nlons=73; nlats=73
dellat = 2.5; dellon = 5.
for line in file.readlines():
   l = line.replace('\n','').split()
   ul.append(float(l[0]))
   vl.append(float(l[1]))
   pl.append(float(l[2]))
u = np.reshape(np.array(ul,np.float32),(nlats,nlons))
v = np.reshape(np.array(vl,np.float32),(nlats,nlons))
p = np.reshape(np.array(pl,np.float32),(nlats,nlons))
lats1 = -90.+dellat*np.arange(nlats)
lons1 = -180.+dellon*np.arange(nlons)
lons, lats = np.meshgrid(lons1, lats1)

# plot vectors in geographical (lat/lon) coordinates.

# north polar projection.
m = Basemap(lon_0=-135,boundinglat=25,
            resolution='c',area_thresh=10000.,projection='npstere')
# create a figure, add an axes.
fig=plt.figure(figsize=(8,8))
ax = fig.add_axes([0.1,0.1,0.7,0.7])
# rotate wind vectors to map projection coordinates.
# (also compute native map projections coordinates of lat/lon grid)
# only do Northern Hemisphere.
urot,vrot,x,y = m.rotate_vector(u[36:,:],v[36:,:],lons[36:,:],lats[36:,:],returnxy=True)
# plot filled contours over map.
cs = m.contourf(x,y,p[36:,:],15,cmap=plt.cm.jet)
# plot wind vectors over map.
Q = m.quiver(x,y,urot,vrot) #or specify, e.g., width=0.003, scale=400)
qk = plt.quiverkey(Q, 0.95, 1.05, 25, '25 m/s', labelpos='W')
cax = plt.axes([0.875, 0.1, 0.05, 0.7]) # setup colorbar axes.
plt.colorbar(cax=cax) # draw colorbar
plt.axes(ax)  # make the original axes current again
m.drawcoastlines()
m.drawcountries()
# draw parallels
delat = 20.
circles = np.arange(0.,90.+delat,delat).tolist()+\
          np.arange(-delat,-90.-delat,-delat).tolist()
m.drawparallels(circles,labels=[1,1,1,1])
# draw meridians
delon = 45.
meridians = np.arange(-180,180,delon)
m.drawmeridians(meridians,labels=[1,1,1,1])
plt.title('Surface Winds Winds and Pressure (lat-lon grid)',y=1.075)
 
# plot vectors in map projection coordinates.

# north polar projection.
m = Basemap(lon_0=-135,boundinglat=25,
            resolution='c',area_thresh=10000.,projection='npstere')
# transform from spherical to map projection coordinates (rotation
# and interpolation).
nxv = 41; nyv = 41
nxp = 101; nyp = 101
spd = np.sqrt(u**2+v**2)
udat, vdat, xv, yv = m.transform_vector(u,v,lons1,lats1,nxv,nyv,returnxy=True)
pdat, xp, yp = m.transform_scalar(p,lons1,lats1,nxp,nyp,returnxy=True)
# create a figure, add an axes.
fig=plt.figure(figsize=(8,8))
ax = fig.add_axes([0.1,0.1,0.7,0.7])
# plot image over map
im = m.imshow(pdat,plt.cm.jet)
# plot wind vectors over map.
Q = m.quiver(xv,yv,udat,vdat) #or specify, e.g., width=0.003, scale=400)
qk = plt.quiverkey(Q, 0.95, 1.05, 25, '25 m/s', labelpos='W')
cax = plt.axes([0.875, 0.1, 0.05, 0.7]) # setup colorbar axes.
plt.colorbar(cax=cax) # draw colorbar
plt.axes(ax)  # make the original axes current again
m.drawcoastlines()
m.drawcountries()
# draw parallels
delat = 20.
circles = np.arange(0.,90.+delat,delat).tolist()+\
          np.arange(-delat,-90.-delat,-delat).tolist()
m.drawparallels(circles,labels=[1,1,1,1])
# draw meridians
delon = 45.
meridians = np.arange(-180,180,delon)
m.drawmeridians(meridians,labels=[1,1,1,1])
plt.title('Surface Winds Winds and Pressure (projection grid)',y=1.075)
plt.show()