title: Line of sight integration of a field along a specific direction
body: <p>Good morning,
  I have a *.npy file where I stored some variables, including OH which is the variable I would like to integrate over the line of sight in Z direction (I have a 3D field.)</p>
  <p>I am new with working with such tools on non-netcdf files. Has someone an advice on how to perform the integration over the line of sight?</p>