[MITgcm-support] Tides in channel model

[钱钰坤]

Hi Ryan,


I have recently tried to add a body forcing to mimic the M2 tide
in a channel model (in 2D x-z plane).  It is quite easy to implement
this by adding some code snippets in 'apply_forcing.F' (see attached).
I found these codes somewhere on the web (but do not remember now).
Its effect can be seen in this animation:
https://github.com/miniufo/InternalWaveBreaking


Notice that it is applied to the first 5 tiles (bi.LT.5).  Hope this helps.



 Best regards 
 
Yu-Kun Qian (钱钰坤) 
Center for Monsoon and Environment Research 
 Department of Atmospheric Sciences
School of Environmental Science and Engineering 
 Sun Yat-sen University 
No. 135 Xingang West Road, Haizhu District 
Guangzhou, 510275, P.R. China 
Tel; 020-84115227 
Email: qianyk at mail3.sysu.edu.cn      


 
 
 
------------------ 原始邮件 ------------------
发件人: "Ryan Abernathey"<ryan.abernathey at gmail.com>;
发送时间: 2021年12月3日(星期五) 晚上10:21
收件人: "MITgcm-support"<mitgcm-support at mitgcm.org>; 

主题: Re: [MITgcm-support] Tides in channel model

 

Thanks for the reply Stanislav! 

In this case, Qiyu is working with a zonally reentrant channel (similar to https://mitgcm.readthedocs.io/en/latest/examples/reentrant_channel/reentrant_channel.html), so there is no open boundary at which to apply tidal forcing. So although it is a small domain, it is more similar to a global model in this respect.


My understanding was that the most common way to force tides in global models was via a specified surface pressure field in the EXF package. (E.g. that's how the LLC4320 simulations were forced.) But I also know there has been a lot of recent work in this area, so maybe there is a simpler option.


Has anyone tried specifying a body force in analytic form using a custom code file? Where would be the right place in the code to insert such a forcing?


Best,
Ryan


On Fri, Dec 3, 2021 at 4:18 AM Stanislav Martyanov <martyanov.sd at gmail.com> wrote:

Hello Qiyu,
the easiest way is to generate a simple grid with constant dx (and/or dy) with one or several open boundaries specified in OBCS_OPTIONS.h (#define ALLOW_OBCS_NORTH, etc). Then, you will need to configure the open boundary conditions (if you specify induced tide) and external forcing (if you want to set geopotantial): i.e. #define OBCS_ALLOW_TIDES in OBCS_OPTIONS.h, and #define EXT_ALLOW_TIDES in EXT_OPTIONS.h


And, of course, you need to set the corresponding filenames with the tidal forcing in data.obcs (and in data.exf, if you want geopotential). Note that only the normal component of tidal current at the open boundaries is currently implemented in the model.


You also should get familiar with the OBCS package where tides can be specified (as open boundary conditions), and with the EXF package where tides can be added through geopotental.


Best,
Stanislav

ср, 1 дек. 2021 г. в 21:50, Qiyu Xiao <qx344 at nyu.edu>:

Dear MITgcm users/developers,


If I want to run a channel model with tides, what is the best way to do that? What functions/variables should I change or is there any package for this purpose? 



Thanks,
Qiyu


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