[MITgcm-support] river runoff

[Jean-Michel Campin]

Hi,

There are few available options for including run-off:

1) the most commonly used is to include just in the surface level,
 as part of surface forcing (substracted to EmP into EmPmR).
 Obviously this approach is not great for deep estuary with high
 vertical resolution (small dz).
 And the effect on sea-level is accounted for with useRealFreshWaterFlux=.TRUE.,
 and in a consistent way for any tracers when Non-Lin Freee-surface is
 used.
 In this case, the run-off can be provide as part of EmPmR or
 separately (e.g., using pkg/exf), but only the run-off that fall
 on ocean grid cell (wet-cell) will be considered.

2) If you want to address the issue of deep estuaries, you can 
  try to prescribe a 3-D run-off input (file: addMassFile loaded into 
  model 2-D array "addMass") using selectAddFluid=1.
  This requires to compile with #define ALLOW_ADDFLUID

  Note that the current code does not provide an option to prescribe
  time dependent "addMass" inflow (but should not be difficult to add).

3) And the last option, as described by Andrea, is to use OBCS. This enable 
  to account, in the momentum budget, for the speed of the incoming run-off.
  Probably useful at very high to high resolution (bot horizontal and vertical)
  but may be not so important at lower resolution.

Cheers,
Jean-Michel

On Wed, Nov 09, 2016 at 08:31:34AM +0100, Andrea Cimatoribus wrote:
> Certainly not the most expert around here, but I have been dealing
> with this lately, so I can try an answer.
> 
> The neatest way to do it is with obcs package, that is, the open
> boundary package. In data.obcs you can define the (vertical) grid
> faces through which you want to apply the discharge (see manual).
> Using the correct grid metric, you can set the discharge velocity to
> match the total volume discharge (and you can easily check if you
> are doing it right using the diagnostic output). The simplest way to
> impose a time-variable discharge and temperature is via the exf
> package, in a new namelist which is provided by the OBCS package,
> something along these lines:
>  &EXF_NML_OBCS
> # OBCS prescribe
>  obcsEstartdate1   = 20080101,
>  obcsEstartdate2   = 010000,
>  obcsEperiod       = 3600.,
>  obcsWstartdate1   = 20080101,
>  obcsWstartdate2   = 010000,
>  obcsWperiod       = 3600.,
>  &
> As far as I understand, the temperature of the discharge must span
> exactly the same time interval and have the same periodicity as the
> velocity.
> The file names containing the data are defined in the data.obcs
> (again, see manual).
> 
> Hope this helps, best,
> 
> Andrea Cimatoribus
> postdoctoral researcher
> EPFL ENAC IIE ECOL
> https://people.epfl.ch/andrea.cimatoribus
> 
> On 09/11/16 03:26, ????????? wrote:
> >Hi
> >
> >I am using mitgcm to simulate SST variation in coastal area with large
> >runoff. Does anyone tell me how to set up the river? How mitgcm deal
> >with river mouth?
> >
> >I've known that the runoff should be added to the freshwater flux EmPmR,
> >but how to represent the effect of a river by gridded runoff data is not
> >clear to me (should the river grid point be contacted with ocean
> >interior or boundary?).
> >
> >It seems that the test cases in mitgcm do not provide enough river
> >information.
> >
> >I'd appreciate any help.
> >
> >
> >------------------
> >Best regards
> >
> >Yu-Kun Qian (?????????)
> >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 <mailto:qianyk at mail2.sysu.edu.cn>
> >
> >
> >
> >
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> >MITgcm-support at mitgcm.org
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> >
> 
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