Du= SQRT(u + Wg**2 ) !include gustiness in wind spd. difference
u10 = Du*LOG(10. _d 0/zo)/LOG(zu/zo)
Ribu=-gravity*zu*(Dt+0.61 _d 0*tta*Dq)/(tta*Du**2)
usr= Du*xkar/(LOG(zu/zo10)-psiu(zu/L10))
IF (Du.GT.10. _d 0) charn=0.011 _d 0
& + (0.018 _d 0-0.011 _d 0)*(Du-10.)/(18.-10.)
IF (Du.GT.18. _d 0) charn=0.018 _d 0
usr=Du*xkar/(LOG(zu/zo)-psiu(zu/L))
Du=SQRT(u**2 + Wg**2) !include gustiness in wind spd.
cdu = tau/Du
_RL Du,Wg,Dt,Dq,u10,zo10,Cd10,Ch10