Fix landmask updating script to avoid excessive memory use

Author: joferkington

utils/plotgrdlandmask.py

@@ -8,8 +8,9 @@
 # this script reads the file generated by grdlandmask, plots it,
 # and saves it in the format that Basemap._readlsmask expects.
 
-# WARNING:  This tends to use excessive amounts of RAM. Do not attempt to run
-# this unless you're on a machine with >=32GB of RAM (yes, 32 Gigabytes).
+UTILS_DIR = os.path.dirname(os.path.abspath(__file__))
+OUTPUT_DIR = os.path.join(UTILS_DIR, '..', 'lib', 'mpl_toolkits',
+                          'basemap', 'data')
 
 # run grdlandmask
 athresh={}
@@ -19,7 +20,7 @@
 athresh['h']=10
 athresh['f']=1
 
-for resolution in ['c']:#,'l','i']:
+for resolution in ['c','l','i','f']:
     for grid in [1.25,2.5,5,10]:
 
         filename = 'grdlandmask%smin_%s.nc' % (grid,resolution)
@@ -31,26 +32,34 @@
 
         # read in data.
         nc = Dataset(filename)
-        print nc.variables.keys()
-        lons = nc.variables['lon'][:]
-        nlons = len(lons)
-        lats = nc.variables['lat'][:]
-        nlats = len(lats)
         lsmask = nc.variables['z'][:].astype(np.uint8)
 
-        # plot
-        fig = plt.figure()
-        m =\
-        Basemap(llcrnrlon=-180,llcrnrlat=-90,urcrnrlon=180,urcrnrlat=90,resolution=resolution,projection='mill')
-        m.drawcoastlines() # coastlines should line up with land/sea mask.
-        m.drawlsmask(land_color='coral',ocean_color='aqua',lsmask=lsmask,lsmask_lons=lons,lsmask_lats=lats,lakes=True)
-        plt.title('%s by %s land-sea mask (resolution = %s) from grdlandmask' %\
-                (nlons,nlats,resolution))
-
         # write out.
-        f = gzip.open('lsmask_%smin_%s.bin' % (grid,resolution),'wb')
-        print lsmask.dtype, lsmask.shape
+        filename = os.path.join(OUTPUT_DIR,
+                                'lsmask_%smin_%s.bin' % (grid, resolution))
+        f = gzip.open(filename, 'wb')
         f.write(lsmask.tostring())
         f.close()
 
+# Plot data for debugging purposes.
+for resolution in ['c','l','i','f']:
+    grid = 10
+    filename = 'grdlandmask%smin_%s.nc' % (grid,resolution)
+
+    nc = Dataset(filename)
+    lsmask = nc.variables['z'][:].astype(np.uint8)
+    lons = nc.variables['lon'][:]
+    lats = nc.variables['lat'][:]
+
+    fig = plt.figure()
+    m = Basemap(llcrnrlon=-180, llcrnrlat=-90,
+                urcrnrlon=180, urcrnrlat=90,
+                resolution=resolution, projection='mill')
+
+    m.drawcoastlines() # coastlines should line up with land/sea mask.
+    m.drawlsmask(land_color='coral', ocean_color='aqua',
+                 lsmask=lsmask, lsmask_lons=lons, lsmask_lats=lats,
+                 lakes=True)
+    plt.title('Land-sea mask (res = %s) from grdlandmask' % resolution)
+
 plt.show()