[RegCNET] about ustar variable in SRF output ...

[Ufuk Utku Turuncoglu (BE)]

Hi All,

I was trying to understand following calculation in Zeng Ocean 
(ocnlib/mod_ocn_zeng.F90)

drag(i) = ustar**2*rhox(i)/uv995

in this case, this variable is used in SRF output as "ustar" (surface 
friction velocity) and its unit is s-1. I think that this is wrong. If i 
analyze the units of the each components of the equation

ustar is friction velocity and unit is m/s
rhox is air density (i think because it is calculate via famous ideal 
gas law formula in mod_slice) and unit is kg/m3
uv995 is lowest level wind speed and unit is m/s

the results field unit must be kg/m2s or Pa or N/m2. The actual variable 
might be the stress (or momentum flux) given as equation 3.31 in RegCM 
Referance Manual or Eq. 21 in Zeng, 1998 paper (but it does not include 
"u" at the end). So, if this is right than the variable name and 
attributes in SRF file is wrong. Please let me know, if anybody has more 
information about it.

Regards,

--ufuk