Hi there, Thanks for sharing the solution! There are not many Mac Monterey F2py users out there haha. I am having the exact same problem, but your fix is not working for me. I think I just don't understand your last step. What command do you type to compile your code? Is that sill the  "f2py -c -m barotropic barotropic.f90 "?? I will deeply appreciate any help! Thanks again Gero