hi,

I found that the defaut set of  iocnrough is 1 in RegCM v4.3.  Actually this formula is not used in RegCM v3. 
Instead the formula in RegCM3 is, the roughness length of momentum: zo= (0.013*ustar*ustar)/egrav+0.11*visa/ustar , following Smith(1988).

!     iocnrough: Zeng Ocean Model Roughness model
!     = 1 ; (0.0065*ustar*ustar)/egrav (the RegCM V3 one)
!     = 2 ; (0.013*ustar*ustar)/egrav+0.11*visa/ustar (the Zeng one)


I wonder why this default set is changed to "(0.0065*ustar*ustar)/egrav".  Is there a reference for this specific equation? 

Thank you very much!



Zhenyu HAN