Surface to atmosphere momentum transfer in WACCM/CAM

[bethproedrou@gmail_com]

Dear all,I am interested in the momentum calculations of the CAM-WACCM model (I am not sure which model performs the calculation). Specifically I wish to study the surface to atmosphere momentum transfer.  I have found the following momentums in the model:UV3d, UW3d, VU, OMEGAV, OMGAOMGA, OMEGAU, UFLX, ZMMTT, ZMMTU, ZMMTVCould someone tell how they are calculated and what exactly are they. There is a description in the masterfields file, but it is too short. Can any of them, or some other parameter I missed be used to study the surface to atmosphere momentum transfer? Thank you in advance for your help,Beth

 

[mmills]

There are CAM history fields pages here:

• http://www.cesm.ucar.edu/models/cesm1.0/cam/docs/ug5_0/hist_flds_fv_cam5.html(CAM5)
• http://www.cesm.ucar.edu/models/cesm1.0/cam/docs/ug5_0/hist_flds_fv_cam4_waccm.html(CAM4-WACCM)

which have metadata (long names) for at least some of these fields. 

 

[bethproedrou@gmail_com]

Dear Mr. Mills,Thank you for your answer. I checked the links that you provided, but they are the same as the ones I have in my possesion and therefore do not provide me with the information I need. Does another source of information, the can provide more details exist? Thank you,Beth

 

[mmills]

None refer to parameterized momentum fluxes, but to explicitly resolved model fields.UV3d, UW3d: These are the resolved fluxes of momentum, and . They arezonally-averaged quantities, so really functions of lat, lev and time only. However,they are stored as 3D fields (hence the 3d subscript) because the outputroutine for CAM does not know how to output zonal means. We use them (along with VT3d)to construct EP fluxes for the WACCM TEM budgets.Can you be more specific about what you are trying to calculate?

 

[mmills]

You may be looking for the TAU outputs, which are the only actual exchanges of momentum between the surface and the atmosphere:

• TAUX                             N/m2                1 A  Zonal surface stress
• TAUY                             N/m2                1 A  Meridional surface stress
• TAUGWX                           N/m2                1 A  Zonal gravity wave surface stress
• TAUGWY                           N/m2                1 A  Meridional gravity wave surface stress
• TAUTMSX                          N/m2                1 A  Zonal      turbulent mountain surface stress
• TAUTMSY                          N/m2                1 A  Meridional turbulent mountain surface stress

 

[bethproedrou@gmail_com]

Thank you very much for the information Mr. Mills. Are the output parameters latitude - longitude - time?I am looking for momentum parameters in the (longitude, latitude, altitude, time) format.

 

[mmills]

The TAU outputs are stresses at the surface, so they have no altitude component.The UV3d and UW3d resolved fluxes of momentum are inherently zonal mean quantities. That is the only way to calculate components of momentum. For more information see:Andrews, D.G., J.R. Holton and C.B. Leovy, 1987: Middle Atmosphere Dynamics. Academic Press, Florida.