In [215]: data = np.random.rand(100,81,121,6,3)

In [216]: labels = np.random.rand(100,2)

In [218]: labels_ext = np.broadcast_to(labels[:,None,None,:,None],(100,81,121,2,3))

In [219]: np.concatenate((data,labels_ext),axis=3).shape
Out[219]: (100, 81, 121, 8, 3)