[MITgcm-support] Using a sponge layer to relax temperature
Jody Klymak
jklymak at uvic.ca
Tue Mar 3 16:28:24 EST 2015
Hi Ashley,
rbcs is pretty flexible. Here is my data.rbcs for runs where I was doing tidal forcing. I didn’t need separate masks for U,V and T, but you might if you are are forcing your plume as temperature only and letting U and V freely evolve.
I don’t know about the hacks Dustin is discussing, but its hard to see why they are necessary as rbcs is so flexible. For me the only disadvantage for big runs is having to specify the fields everywhere for every rbcsForcingPeriod.
Cheers, Jody
# RBCS package parameters:
&RBCS_PARM01
#------------------------------------------------------------------------------
# switches
#------------------------------------------------------------------------------
useRBCtemp=.TRUE.,
useRBCvVel=.TRUE.,
useRBCuVel=.TRUE.,
# useRBCsalt=.TRUE.,
#------------------------------------------------------------------------------
#- relaxation times
# This is the timescale where "sponge=1".
#------------------------------------------------------------------------------
tauRelaxU=120000.,
tauRelaxV=120000.,
tauRelaxT=120000.,
#------------------------------------------------------------------------------
# masks - #1 and #2 = T,S , #3 = tracers ;
# masks U,V have explicit name - if left out then TMask = used
#------------------------------------------------------------------------------
# Probably need different U and V masks because they are on a slightly different
# grid
relaxMaskFile='spongeweight.bin',
# relaxMaskUFile='usponge.bin',
# relaxMaskVFile='vsponge.bin',
#------------------------------------------------------------------------------
# files containing relaxation flds have explicit name
#------------------------------------------------------------------------------
relaxTFile='Tforce.bin',
relaxUFile='Uforce.bin',
relaxVFile='Vforce.bin',
#------------------------------------------------------------------------------
rbcsIniter=0,
# 1/24 tidal cycle
rbcsForcingPeriod=1860.,
rbcsForcingCycle=44640.,
/
> On 3 Mar 2015, at 11:28 AM, Stroman, Ashley <acs08g at my.fsu.edu> wrote:
>
> Hi Dustin.
>
> After looking through the code, it appears that the modified rbcs package from Siascia is only for multiple relaxation fields regarding momentum and not temperature. So if I wanted to use this in my simulations, then I’d have to rewrite the routine to also include temperature, which might be doable. Not sure if it’s easiest to rewrite the rbcs code to include multiple relaxations fields for temperature or just use the OBCS package to use a sponge layer though.
>
> Best,
> Ashley
>> On Mar 2, 2015, at 1:44 PM, Dustin Carroll <dcarroll at uoregon.edu <mailto:dcarroll at uoregon.edu>> wrote:
>>
>> Hi Ashley,
>>
>> Ryan has good advice here. if you need to relax your plume and boundary temperature at different timescales, Roberta Sciascia added a nice mod. to RBCS pkg under MITgcm_contrib/sciascia/rbcs that allows for multiple RBCS fields with independent relaxation times. You can then have multiple masks / relaxation files (i.e., one for your plume and one for the boundaries).
>>
>> Dustin
>>
>>> On Mar 2, 2015, at 10:31 AM, Stroman, Ashley <acs08g at my.fsu.edu <mailto:acs08g at my.fsu.edu>> wrote:
>>>
>>> Well, I already use the RBCS package to force a plume in the middle of the domain, so I didn’t try using the RBCS package for the temperature on the boundaries because I wasn’t sure if you could use the RBCS package twice in one simulation.
>>>
>>> -Ashley
>>>> On Mar 2, 2015, at 1:28 PM, Ryan Abernathey <ryan.abernathey at gmail.com <mailto:ryan.abernathey at gmail.com>> wrote:
>>>>
>>>> Just wanted to point out, as a possible alternative, the RBCS package.
>>>> http://mitgcm.org/public/r2_manual/latest/online_documents/node237.html <http://mitgcm.org/public/r2_manual/latest/online_documents/node237.html>
>>>>
>>>> RBCS allows you to relax to model fields to some prescribed field (with a variable relaxation rate) throughout the whole domain. It is somewhat simpler to use and understand than OBCS.
>>>>
>>>> If you don't need actual open boundary features (e.g. Orlanski, inflow / outflow), RBCS is more than adequate for making sponge layers.
>>>>
>>>> -Ryan
>>>>
>>>> On Mon, Mar 2, 2015 at 12:56 PM, Stroman, Ashley <acs08g at my.fsu.edu <mailto:acs08g at my.fsu.edu>> wrote:
>>>> Hi Dustin.
>>>>
>>>> I have two specific questions regarding my problem:
>>>>
>>>> 1.) Is it possible to use Orlanski for momentum on the boundaries, while also using a sponge layer to restore temperature to the initial conditions on the boundaries? I’m not sure if both are allowed, and I’ve had no luck finding this answer online.
>>>>
>>>> 2.) What is the difference between useOBCSsponge and OBCSsponge_Theta in the data.obcs file? My thought is that the latter is specifically used for theta while the former is not, but I am not 100% positive. There’s not much information on the latter parameter except that it turns on the theta sponge along the boundaries, so I’m not sure if the parameter is used, 1) what it specifically means, and 2) what is additionally required.
>>>>
>>>> Thanks.
>>>> Ashley
>>>>> On Feb 27, 2015, at 8:06 PM, Dustin Carroll <spanishcastlemagik at gmail.com <mailto:spanishcastlemagik at gmail.com>> wrote:
>>>>>
>>>>> Hi Ashley,
>>>>>
>>>>> Can you provide a bit more information on the problem you are having? I find that the more specific you are, the easier it is for people to help on this support group.
>>>>>
>>>>> Section 6.3.1 in the docs (see below) describes how to set up your data.obcs file, also look at verification/exp4 for an example w/ open boundaries.
>>>>> http://mitgcm.org/public/r2_manual/latest/online_documents/node236.html <http://mitgcm.org/public/r2_manual/latest/online_documents/node236.html>
>>>>>
>>>>> If you want to restore your boundaries to the prescribed ICs then you’ll need to generate binary files for each boundary that is specified in data.obcs,
>>>>>
>>>>> Cheers,
>>>>> Dustin
>>>>>
>>>>>
>>>>>> On Feb 27, 2015, at 11:56 AM, Stroman, Ashley <acs08g at my.fsu.edu <mailto:acs08g at my.fsu.edu>> wrote:
>>>>>>
>>>>>> Hello.
>>>>>>
>>>>>> I am wanting to use the OBCS package to implement a sponge layer on the boundaries to relax temperature to the initial conditions. I am having trouble finding what is needed in terms of the data.obcs file as well as any any additional binary files for temperature that are required. Can someone shed some light on this? Thanks.
>>>>>>
>>>>>> Best,
>>>>>> Ashley Stroman
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--
Jody Klymak
http://web.uvic.ca/~jklymak/
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