Help about boundaries sponge layer

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lalvarez
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Joined: Wed Feb 03, 2010 6:59 pm
Location: Universidad Autonoma de Baja California Sur

Help about boundaries sponge layer

#1 Unread post by lalvarez »

Hello to All

I have got some results from my modeling in the California Current, but as you may see (attached figures are monthly mean surface velocities for january and may 1996), I still have some problems with my north, south & west boundaries, so i'm looking for help in order to reduce this problems and get more involved about how to set an sponge layer or boundary.

I attach also my *.in & *.h files

Thanks in advance & have a nice day
Attachments
leo.in
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leo.h
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Vel_199605.jpg
Vel_199601.jpg

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kate
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Re: Help about boundaries sponge layer

#2 Unread post by kate »

I see that you are using clamped boundaries. What is it that you are clamping to? Is it such a good match that you don't want your model to have wiggle room? I have been using the RadNud boundary condition since it came out with timescales somewhat similar to your TNUDG and OBCFAC values. You would have to change M3NUDG and so forth from zero if you switch to RadNud.

A sponge layer is a band of increased horizontal friction and diffusivity. It's not obvious that it would improve your solution.

lalvarez
Posts: 104
Joined: Wed Feb 03, 2010 6:59 pm
Location: Universidad Autonoma de Baja California Sur

Re: Help about boundaries sponge layer

#3 Unread post by lalvarez »

Hello Kate

Thanks a lot for your answer, please let me understand it slowly; this is how i have my LBC now

Code: Select all

!                   W       S       E       N
!                   e       o       a       o
!                   s       u       s       r
!                   t       t       t       t
!                           h               h
!
!                   1       2       3       4

   LBC(isFsur) ==   Cha     Cha     Clo     Cha         ! free-surface
   LBC(isUbar) ==   Fla     Fla     Clo     Fla         ! 2D U-momentum
   LBC(isVbar) ==   Fla     Fla     Clo     Fla         ! 2D V-momentum
   LBC(isUvel) ==   Cla     Cla     Clo     Cla         ! 3D U-momentum
   LBC(isVvel) ==   Cla     Cla     Clo     Cla         ! 3D V-momentum
   LBC(isMtke) ==   Gra     Gra     Clo     Gra         ! mixing TKE

   LBC(isTvar) ==   Cla     Cla     Clo     Cla \       ! temperature
                    Cla     Cla     Clo     Cla         ! salinity
What you are suggesting me to do is to change the clamped ones, these are:

Code: Select all

LBC(isUvel) ==   Cla     Cla     Clo     Cla         ! 3D U-momentum
LBC(isVvel) ==   Cla     Cla     Clo     Cla         ! 3D V-momentum
and
C(isTvar) ==   Cla     Cla     Clo     Cla \       ! temperature
               Cla     Cla     Clo     Cla         ! salinity
for the RadNud mode (correct me if i'm wrong), so that would be:

Code: Select all

LBC(isUvel) ==   Sch     Sch     Clo     Sch         ! 3D U-momentum
LBC(isVvel) ==   Sch     Sch     Clo     Sch         ! 3D V-momentum
and
LBC(isTvar) ==   Sch     Sch     Clo     Sch \       ! temperature
                 Sch     Sch     Clo     Sch         ! salinity
Another question, What are values you use for the:

Code: Select all

! Nudging/relaxation time scales, inverse scales will be computed
! internally, [1:Ngrids].

       TNUDG == 100.0d0  100.0d0           ! days
       ZNUDG == 0.0d0                      ! days
      M2NUDG == 0.0d0                      ! days
      M3NUDG == 0.0d0                      ! days
Thanks in advance & have a nice weekend

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kate
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Re: Help about boundaries sponge layer

#4 Unread post by kate »

Close, but this is what I typically use:

Code: Select all

   LBC(isFsur) ==   Che     Che     Che     Che         ! free-surface
   LBC(isUbar) ==   Shc     Shc     Shc     Shc         ! 2D U-momentum
   LBC(isVbar) ==   Shc     Shc     Shc     Shc         ! 2D V-momentum
   LBC(isUvel) ==   RadNud  RadNud  RadNud  RadNud      ! 3D U-momentum
   LBC(isVvel) ==   RadNud  RadNud  RadNud  RadNud      ! 3D V-momentum
   LBC(isMtke) ==   Clo     Clo     Clo     Clo         ! mixing TKE

   LBC(isTvar) ==   RadNud  RadNud  RadNud  RadNud \    ! temperature
                    RadNud  RadNud  RadNud  RadNud \    ! salinity
and

Code: Select all

       TNUDG == 2*360.0d0                    ! days
       ZNUDG == 360.0d0                      ! days
      M2NUDG == 360.0d0                      ! days
      M3NUDG == 360.0d0                      ! days

! Factor between passive (outflow) and active (inflow) open boundary
! conditions, [1:Ngrids]. If OBCFAC > 1, nudging on inflow is stronger
! than on outflow (recommended).

      OBCFAC == 120.0d0                      ! nondimensional
Now, there are domains in which I still have boundary currents. I think it depends on the quality of the fields being used for boundary conditions. Daily ROMS fields from a larger domain are a better match than weekly SODA fields. Sometimes I use daily HYCOM fields. What do you have?

Ahumada
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Location: Universidad del Mar

Re: Help about boundaries sponge layer

#5 Unread post by Ahumada »

Hi Leo,

The following are good references for this topic:

Marchesiello et al. (2001) Open boundary conditions for long-term integration of regional oceanic models. Ocean Modelling, 3, 1-20.

Mason et al. (2010) Procedures for offline grid nesting in regional ocean models. Ocean Modelling, 35, 1-15.

Cheers!

Miguel Angel

lalvarez
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Joined: Wed Feb 03, 2010 6:59 pm
Location: Universidad Autonoma de Baja California Sur

Re: Help about boundaries sponge layer

#6 Unread post by lalvarez »

Hola Miguel

Thanks a lot for those referencies i´m reading them.

Have a nice day my Friend

lalvarez
Posts: 104
Joined: Wed Feb 03, 2010 6:59 pm
Location: Universidad Autonoma de Baja California Sur

Re: Help about boundaries sponge layer

#7 Unread post by lalvarez »

Hello Kate

Thanks a lot for your guiding, i´m running my domain with values you posted for the LBC´s.

I still have some wierd things happening on my boundaries, specially on the west one, I hope tomorrow will post some graphic results about daily salinity, temperature and velocities.

Well i´m forcing with:
Tides are TPOX 7
Surface and LBC (monthly T°c,Sal, Rad, etc) are WOA 2005
Bathymetry is ETOPO1
Surface wind is CCMP (6 hours)

I hope this is what you refer to.

Have a nice day

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kate
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Re: Help about boundaries sponge layer

#8 Unread post by kate »

Yes, that's what I meant.
Surface and LBC (monthly T°c,Sal, Rad, etc) are WOA 2005
Many, many years ago we used monthly T,S climatologies on the boundary and didn't get very good results. Is there some reason you can't use something better? HYCOM, perhaps? Anyone else have good luck with a climatology?

lalvarez
Posts: 104
Joined: Wed Feb 03, 2010 6:59 pm
Location: Universidad Autonoma de Baja California Sur

Re: Help about boundaries sponge layer

#9 Unread post by lalvarez »

Hello Kate

We have not try the HYCOM info, I'm sure it must have better results as you say.

By now we are facing another problem, we expand our domain fron 500km to 1000km offshore and when making the climatological files, it seems the _clim.nc file gets too big (>3 G) and can't be handeled.

My question is: Can the _clim.nc file be divided in 2 (such as _clim1.nc & _clim2.nc) with succesive ending-starting dates? I saw something alike here in the forum, but cannot remember well where it was.

Any hint will be heplful

Have a nice day

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kate
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Re: Help about boundaries sponge layer

#10 Unread post by kate »

Yes, you can split the climatology files in time, as long as they are not using cyclic time.

Modern 64-bit systems can handle files larger than 2 GB, though, so cyclic time should be possible. Just make sure your netcdf files are created in 64-bit mode, or maybe compressed netcdf4 mode.

lalvarez
Posts: 104
Joined: Wed Feb 03, 2010 6:59 pm
Location: Universidad Autonoma de Baja California Sur

Re: Help about boundaries sponge layer

#11 Unread post by lalvarez »

Hello Kate

Thanks for your answer and Yes we are working on 64 bits.

I will try making my files smaller, i'll make a 1 year sequence and try making a 6, 4 and 3 months files and see what happen

Have a nice day

lalvarez
Posts: 104
Joined: Wed Feb 03, 2010 6:59 pm
Location: Universidad Autonoma de Baja California Sur

Re: Help about boundaries sponge layer

#12 Unread post by lalvarez »

Hello Kate

We have finally change to HYCOM daily data for the forcing and OBC´s, but I still have one question about a suggestion of yours.

We are doing a 455 days run and my question is, How do I must handle the TNUDG, ZNUDG, M2NUDG, M3NUDG and OBCFAC parameters in order to adjust them to my 455 day run?

TNUDG == 2*360.0d0 ! days
ZNUDG == 360.0d0 ! days
M2NUDG == 360.0d0 ! days
M3NUDG == 360.0d0 ! days

! Factor between passive (outflow) and active (inflow) open boundary
! conditions, [1:Ngrids]. If OBCFAC > 1, nudging on inflow is stronger
! than on outflow (recommended).

OBCFAC == 120.0d0 ! nondimensional


Thanks in advance and have a nice day

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kate
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Re: Help about boundaries sponge layer

#13 Unread post by kate »

Is there some reason you want to change those values? Are you unhappy with the solution? They are simply time-scales of nudging and shouldn't change with the length of your run.

lalvarez
Posts: 104
Joined: Wed Feb 03, 2010 6:59 pm
Location: Universidad Autonoma de Baja California Sur

Re: Help about boundaries sponge layer

#14 Unread post by lalvarez »

Hello Kate

Actually there´s no reason I just had the doubt

Thanks a lot

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