[MITgcm-support] Unstructured open boundaries

Estanislao Gavilan Pascual-Ahuir dramauh at hotmail.com
Tue Sep 24 23:47:50 EDT 2019


Hi everyone,

I figured out the way to do it. I am no sure if anyone else wants to impose this kind of boundary, so I will leave a short in introduction here. After filling the code with print comments I found out that the main issue was in obcs_check.F. It seems that if a boundary it is located in a corner, this file thinks that there is two open boundaries in the same cell grid.

So here we have a open boundary. The empty and the filled squares are boundary and land grid points, respectively. The + represents the open boundary line on the model. Note that the point (1,2) is not a open boundary point, therefore we have 3 grid cell in row 1 and 1 grid cell in row 2 that are open boundary points. Among these points the model will be confused at the point (2,2) because it will think that there is a south and west boundary point at the same time. This will happen even if you specify the  OB_Iwest=0. For some reason the model is still thinking that there is a western open boundary there.

////////////|+++++++++
/////////////|                  |+
/////////////|                  |+                                                             j=2
/////////////|                  |+
////////////|                   |+++++++++++++++++++++++
/////////////|/////////////|                  |                  |                  |
/////////////|/////////////|                  |                  |                  |       j=1
/////////////|/////////////|                  |                  |                  |
/////////////|/////////////|                    |                    |                    |
      i=1              i=2               i=3             i=4             i=5

Knowing this, the data.obcs have to be specified in this way

&OBCS_PARM01
 OB_Iwest=1*0,1*2,
 OB_Jsouth=1*0,1*2,3*1,

Kind regards,

PS: I could not find anything in the manual, so I am no sure if it worth to write a small section about this on the website.


Today's Topics:

   1. Unstructured open boundaries (Estanislao Gavilan Pascual-Ahuir)


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Message: 1
Date: Wed, 18 Sep 2019 02:34:04 +0000
From: Estanislao Gavilan Pascual-Ahuir <dramauh at hotmail.com>
To: "mitgcm-support at mitgcm.org" <mitgcm-support at mitgcm.org>
Subject: [MITgcm-support] Unstructured open boundaries
Message-ID:
        <DB8PR04MB700217A224EAAA4996C889F8A98E0 at DB8PR04MB7002.eurprd04.prod.outlook.com>

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Dear Community,

A few weeks ago I found a post in our email list about this but I cannot find it again. I would like to open boundaries in different rows.. For example I was thinking to do this but it is wrong.. As you can read I want to open 19 points in middle of the first and last row. Then I want to open 3 points and then other three points in the second row and the before the last row. I think it can be done but I am no doing something correctly. The forcing files are a single row with 81 points where your can find the specific values from the 29th to the 53rd column. Thanks in advance for your help.

Kind regards,

Estanislao

# Open-boundaries
 &OBCS_PARM01
 OBCSfixTopo=.FALSE.,
 OB_Ieast=0,
 OB_Iwest=0,
 OB_Jnorth=31*0,19*-1,31*0,
 OB_Jnorth=28*0,3*80,19*0,3*80,28*0,
 OB_Jsouth=28*0,3*2,19*0,3*2,28*0,
 OB_Jsouth=31*0,19*1,31*0,
 useOBCSprescribe = .TRUE.,
 OBNvFile = 'OBzonaloutV05.bin',
 OBSvFile = 'OBzonalinV05.bin',
 OBNuFile = 'OBmeridoutU05.bin',
 OBSuFile = 'OBmeridinU05.bin',


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