Set two matplotlib imshow plots to have the same color map scale
First you need to define the min and max of the color range you want to use. In this example it is the min and max of both arrays you are plotting. Then use these values to set the range of the imshow color code.
import numpy as np
def show_field(field1,field2):
combined_data = np.array([field1,field2])
#Get the min and max of all your data
_min, _max = np.amin(combined_data), np.amax(combined_data)
fig = plt.figure()
ax = fig.add_subplot(2, 1, 1)
#Add the vmin and vmax arguments to set the color scale
ax.imshow(field1,cmap=plt.cm.YlGn, vmin = _min, vmax = _max)
ax.set_adjustable('box-forced')
ax.autoscale(False)
ax2 = fig.add_subplot(2, 1, 2)
ax2.set_adjustable('box-forced')
#Add the vmin and vmax arguments to set the color scale
ax2.imshow(field2,cmap=plt.cm.YlGn, vmin = _min, vmax = _max)
ax2.autoscale(False)
plt.show()