A question about the calculation of Stokes velocity drift on the surface

[Agoni00]

In the program w3iogomd.ftn, we can see the calculation of the Stokes drift speed, but I found that the calculated speed is too small, then I uncommented these two lines and the speed is not too small, so It seems that uncommenting the calculated speed is more accurate, I want to know why the source program to the two line commented out? See the following figure for the source code details.

[CarstenHansen]

You also created an issue #776 from this discussion. I suggest that you share your experience in issue #669, where @qingli411 is working in on making the Stokes tail extension an optional feature.