掩盖海洋上的插值数据

Question

我需要屏蔽海洋/水上的数据，以便只有陆地上的数据可见。下面是我正在使用的matplotlib脚本示例。此数据通过griddata()进行插补。

Python脚本：

def mapformat():

  m = Basemap(llcrnrlon=-85,llcrnrlat=36.5,urcrnrlon=-64,urcrnrlat=47.5,
        projection='lcc',lat_1=33,lat_2=45,lon_0=-70,lon_1=-60, resolution='h')
  # resolution c, l, i, h, f in that order

  m.drawmapboundary(fill_color='aqua', zorder=-1)
  m.fillcontinents(color='green', lake_color='aqua', zorder=0)

  m.drawcounties(color='0.1', linewidth=0.05, antialiased=True)
  m.drawcoastlines(color='0.0', linewidth=0.25, antialiased=True)
  m.drawcountries(color='0.0', linewidth=0.5, antialiased=True)
  m.drawstates(color='0.0', linewidth=0.25, antialiased=True)
  #m.drawparallels(np.arange(35.,45.,5), labels=[1,0,0,1], dashes=[1,1], linewidth=0.25, color='0.5')
  #m.drawmeridians(np.arange(0., 360., 5.), labels=[1,0,0,1], dashes=[1,1], linewidth=0.25, color='0.5')

  return m

data = np.loadtxt('/home/.../.../.../maxs', delimiter=',', skiprows=1)

m = mapformat()

dx = 0.25

grid_x, grid_y = np.mgrid[-85:-60:dx, 34:50:dx] #Northeast

temp = data[:,0]

#print temp

figure = plt.gcf() # get current figure
figure.set_size_inches(8, 4.5)

grid_z = griddata((data[:,2],data[:,1]), data[:,0], (grid_x,grid_y), method='cubic')

x,y = m(data[:,2], data[:,1]) # flip lat/lon

grid_x,grid_y = m(grid_x,grid_y)

#m.plot(x,y, 'ko', markersize=2)

for i in range(len(temp)):
    fmt=r"%.f" % (temp[i])
    #plt.text(x[i], y[i], fmt, va="center", ha="center", fontsize='12')
    plt.annotate(fmt,xy=(x[i], y[i]), xytext=None, va="center", ha="center", fontsize="3")

    clevs1 =[-30,-29,-28,-27,-26,-25,-24,-23,-22,-21, -20,    -19,-18,-17,-16,-15,-14,-13,-12,-11,-10,-9,-8,-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,
19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,
58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,
98,99,100,101,102,103,104,105,106,107,108,109,110]

custom = mcolors.LinearSegmentedColormap.from_list( 'own2', [ltsilver,medblue,darkpurple,brightpink,medred,white,
medblue,cyan,medgreen,yellow,orange,red,darkred,darkpeach,ltsilver] )

m.contourf(grid_x,grid_y,grid_z,clevs1,cmap=custom)

剧情示例：

我已经读过可以通过底图中的is_land实现屏蔽，但我不确定它是否适用于插值数据。此外，海洋/水域上没有数据点。

Answer 1

我记得尝试做类似的事情。我会发布我能做的，但这来自于挖掘旧代码。

关键步骤似乎是：

1. 获得良好的陆地/海洋边界
2. 从中制作一个Polygon对象
3. 将多边形添加到轴
4. 使用关键字clip_path和clip_on。
绘制数据

我的特定代码段是

USPatch = mpl.patch.Polygon(USXY, facecolor='none', edgecolor='none')
ax.add_patch(USPatch)
im = bm.pcolormesh(lonE, latE, data,
                   ax=ax, clip_path=USPatch, clip_on=True, zorder=1)
im.set_clip_path(USPatch)

其中USXY是美国边境的numpy数组，bm是我的Basemap对象。我想我从USXY获得了bm.drawcoastlines().get_segments()，但我不知道（或者不记得）如何从线段转到良好的完整边界。

不幸的是，我还没有能够从旧代码的片段中做出最小的工作示例。尝试解析this on Basemap and clipping。