zo = 0.0001 _d 0
u10 = Du*LOG(10. _d 0/zo)/LOG(zu/zo)
zo=charn*usr*usr/gravity + 0.11 _d 0*visa/usr !after Smith 1988
zo=(50./twoPI)*lwave*(usr/cwave)**4.5 _d 0
zo=1200. _d 0*wavesh(i,j,bi,bj)*(wavesh(i,j,bi,bj)/lwave)**4.5
rr=zo*usr/visa
& ' rr,zo,usr,visa=', rr, zo, usr, visa
& ' ln(zu/zo),psu,diff,zL*=', LOG(zu/zo), psu, LOG(zu/zo)-psu,
usr=Du*xkar/(LOG(zu/zo)-psiu(zu/L))
_RL zo,zot,zoq,RR,zL