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Offline MOC calculation

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younglan.shin@...
Offline MOC calculation

Hi.

When calculating ocean meridional overturning circulation offline from pop history files, does it matter if I use VVEL instead of WVEL? (I know that for the modern pop configuration for CCSM3, both variables are used for calculating MOC for the Atlantic). My configuration is the simplest one, the ocean covered configuration. My question is whether the calulated MOC values are the same (or equivalent ) between the case of using VVEL and the case of using WVEL. Any clarification on this MOC matter will be greatly appreciated.

Thanks and Happy holidays!!

young

bates

Are you aware that there is a variable (called MOC) output by CCSM3? You'll find it in the ocean history files. If there is a reason you are calculating this variable offline, write back and I'll look into your question.

younglan.shin@...

bates wrote:

Are you aware that there is a variable (called MOC) output by CCSM3? You'll find it in the ocean history files. If there is a reason you are calculating this variable offline, write back and I'll look into your question.

Hi.

Thank you for your reply. Dr. Shields from NCAR gave me good advice on how to set up POP and sent me the fortran code for offline moc calculation.

In order to calculate MOC online (for my (paleo)geographical configuration), I needed to modify 'lat_aux_grid_type' , 'lat_aux_begin', 'lat_aux_end', 'n_lat_aux_grid' and 'n_transport_reg' in my pop_in.

I also calculated MOC offline using the fortran code. I calculated two differen ways: using (1)VVEL and UVEL and (2) WVEL . These two results were almost identical. Just for my curiosity, in your opinion, which one produces more accurate results?

Thank you. Also, I'd like to thank Dr. Shields' help.

Young

bates

I have spoken with an MOC expert here at NCAR (I am the ocean model science liaison here at NCAR) and here is the answer I got to your question:

Either method you use should be near equivalent in accuracy. MOC can be computed either by
integrating VVEL or by integrating WVEL appropriately. Either way will work in the Atlantic interior; BUT, at the southern boundary of the Atlantic (30S), VVEL must be used to get inflow/outflow through the southern latitude wall.

Hope this helps!
Susan

lehner@...

Young wrote:

Thank you for your reply. Dr. Shields from NCAR gave me good advice on how to set up POP and sent me the fortran code for offline moc calculation.

In order to calculate MOC online (for my (paleo)geographical configuration), I needed to modify 'lat_aux_grid_type' , 'lat_aux_begin', 'lat_aux_end', 'n_lat_aux_grid' and 'n_transport_reg' in my pop_in.

I also calculated MOC offline using the fortran code. I calculated two differen ways: using (1)VVEL and UVEL and (2) WVEL . These two results were almost identical. Just for my curiosity, in your opinion, which one produces more accurate results?

Is this fortran code available on the NCAR homepage or through some other channels?

Appreciate it,
Flavio

Flavio Lehner
Climate and Environmental Physics & Oeschger Centre for Climate Change Research
Physics Institute, University of Bern
http://www.climate.unibe.ch/~lehner

bates

I am unable to attach fortran code to this forum. I can email it to you individually.
Susan

zdliu@...

Dear Susan,

Now I want to get the fortran code for offline MOC calculation , so would you like to email it to me? (and my email is : zdliu@ouc.edu.cn)

And I am using CESM1.0.

Thanks.

zedong

ZEDONG LIU
OUC & QNLM
Email:zdliu@ouc.edu.cn

bates

Hi Zedong,

There is code written in NCL that will do the MOC calculation for you. This will work with the newer CESM code. The documentation for that code is here:

http://www.ncl.ucar.edu/Document/Functions/Built-in/moc_globe_atl.shtml

The documentation also includes an example NCL script to make use of this function.


Susan


Note: For those users still using CCSM3, this code can be modified to work with CCSM3 output as well.

zdliu@...

Dear Suan,

Thank you very much. I knew the NCL script, and I have used it for calculation once. But there is a question, for example, I use the tx0.1v2 POP, there is no MOC output, so I cannot find the template of MOC and its associated auxilary latitudinal grid(lat_aux_grid). Before, I choosed some arbitrary lat_aux_grid, such as (-90:0.1:90), but the result of MOC is very different with the grid I choosed. So would you give me some comments about how to choose the lat_aux_grid?

And also I have noticed that in the cesm/pop code there are some routines to compute some diagnostics on an auxilary latitudinal grid, so now I am now working hard at the fortran code.

Thanks again.

zedong

131004

ZEDONG LIU
OUC & QNLM
Email:zdliu@ouc.edu.cn

zdliu@...

 

 

ZEDONG LIU
OUC & QNLM
Email:zdliu@ouc.edu.cn

wanlingfeng_123@...

Dear everyone

   I want calculate the AMOC change with time use the CESM/POP output, but i do not know which variable is used, BSF or MOC?

wan lingfeng

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