bottom stress in ROMS3.0

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xqzhang · #1 Unread post by **xqzhang** » Mon Sep 03, 2007 8:01 pm

Hi everyone,

Does anyone know where the bottom stress is calculated in ROMS 3.0?
Is there a way that I can turn it off if I want a slip bottom boundary condition?

Thanks,

jcwarner · #2 Unread post by **jcwarner** » Tue Sep 04, 2007 12:38 am

there are 3 types of bottom stress options in ROMS:
UV_LOGDRAG use to turn ON or OFF logarithmic bottom friction
UV_LDRAG use to turn ON or OFF linear bottom friction
UV_QDRAG use to turn ON or OFF quadratic bottom friction

The user needs to select one. All 3 are computed in ROMS/Nonlinear/set_vbc.F. I think the program will yell at you if you do not select at least one, so choose one. The coefficients for the log, linear, or quadratic stress values are set in the ocean.in file. You can set the apppropriate coefficient to = 0. However there are still minimum and maximum stress values. See for example in set_vbc we have:

Code: Select all

wrk(i,j)=MIN(Cdb_max,MAX(Cdb_min,cff2))

So there are min and max values for the bottom stress. The cdb_min and cdb_max are set in
ROMS/Modules/mod_scalars.F.

xqzhang · #3 Unread post by **xqzhang** » Tue Sep 04, 2007 12:57 am

Thank you very much for your comments.
This helps a lot.

xqzhang · #4 Unread post by **xqzhang** » Tue Sep 04, 2007 2:01 am

I got a follow-up question.

I looked at set_vbc.F and saw that sustr and svstr were calculated
in this program using UV_LOGDRAG, UV_LDRAG or UV_QDRAG.
I found that sustr and svstr could also be defined analytically in
ROMS/Functions/ana_smflux.f. Which one really counts if I defined
both UV_QDRAG and ANA_SMFLUX in my code?

jcwarner · #5 Unread post by **jcwarner** » Tue Sep 04, 2007 2:08 am

The variables sustr and svstr are only computed in set_vbc if you have the iceshelf activated. Else, the sustr and svstr are computed in ana_smflux if you have ana_smflux activated, or they are read in from a netcdf file.
I forgot to mention before that it is not highly recomended to run the model with no bottom stress, but i suppose you are trying to compare to some analytical solution or something.

so:
uv_qdrag is for bustr and bvstr.
ana_smflux is for sustr and svstr.

xqzhang · #6 Unread post by **xqzhang** » Tue Sep 04, 2007 2:16 am

I see. Thanks again.

meiw · #7 Unread post by **meiw** » Sun Mar 09, 2008 4:11 am

Hi John,

I wonder why it is not recommended to run ROMS without bottom stress. Thanks.

Wei

jcwarner wrote:The variables sustr and svstr are only computed in set_vbc if you have the iceshelf activated. Else, the sustr and svstr are computed in ana_smflux if you have ana_smflux activated, or they are read in from a netcdf file.
I forgot to mention before that it is not highly recomended to run the model with no bottom stress, but i suppose you are trying to compare to some analytical solution or something.

so:
uv_qdrag is for bustr and bvstr.
ana_smflux is for sustr and svstr.

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