River bottom salinity too high

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WANGQIAN
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Joined: Tue Aug 22, 2017 5:38 pm
Location: Second Institute of Oceanography

River bottom salinity too high

#1 Post by WANGQIAN » Thu Aug 02, 2018 3:14 pm

Hi everyone
I make river forcing file and make salinity zero every time in this file.
And in .in file like this

LuvSrc == T ! horizontal momentum transport
LwSrc == F ! volume vertical influx

! Logical switches (TRUE/FALSE) to activate tracers point Sources/Sinks
! (like river runoff) and to specify which tracer variables to consider:
! [1:NAT+NPT,Ngrids]. See glossary below for details.

LtracerSrc == F T ! temperature, salinity, inert

In .log file ,OceanM reads data correctly, like this

GET_NGFLD - river runoff mass transport, 2013-03-01 00:00:00.00
(Grid= 01, Rec=0000003, Index=2, File: scs_river.nc)
(Tmin= 0.0000 Tmax= 1795.0000) t = 59.0000
(Min = 2.52794889E+02 Max = 2.24987452E+03)
GET_NGFLD - river runoff salinity, 2013-03-01 00:00:00.00
(Grid= 01, Rec=0000003, Index=2, File: scs_river.nc)
(Tmin= 0.0000 Tmax= 1795.0000) t = 59.0000
(Min = 0.00000000E+00 Max = 0.00000000E+00)

But in avg.nc file, at mouth of river, the bottom salinity is very high, more than 100!
Absolutely , my model has blew up. But I don't know whats wrong with me.
Can anyone help me ?
My river forcing file is monthly ,but my forcing file is 3-hour step.
Attachments
this picture shows bottom salinity,and the curve shows salinity changing with s_rho.
this picture shows bottom salinity,and the curve shows salinity changing with s_rho.
QQ图片20180802231056.png (58.99 KiB) Viewed 1592 times

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kate
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Re: River bottom salinity too high

#2 Post by kate » Thu Aug 02, 2018 5:06 pm

I don't know about the salt, but you need to set the temperature tracer on inflow as well. The only time you can skip setting the river tracers is when your rivers all flow outward. If you don't on inflow, the model will go unstable.

WANGQIAN
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Joined: Tue Aug 22, 2017 5:38 pm
Location: Second Institute of Oceanography

Re: River bottom salinity too high

#3 Post by WANGQIAN » Fri Aug 03, 2018 2:29 am

kate wrote:I don't know about the salt, but you need to set the temperature tracer on inflow as well. The only time you can skip setting the river tracers is when your rivers all flow outward. If you don't on inflow, the model will go unstable.
Thank you kate , I will try this.
But in wikiroms/river_runoff, it says:
The introduction of tracer fluxes at point sources/sinks is activated with a second set of logical flags.

! Logical switches (TRUE/FALSE) to activate tracers point Sources/Sinks
! (like river runoff) and to specify which tracer variables to consider:
! [1:NAT+NPT,Ngrids]. See glossary below for details.

LtracerSrc == F T ! temperature, salinity, inert ...
This example says impose salinity but not temperature conditions in the river inflow. This requires that variable "river_salt" is present in the river forcing NetCDF, or is set in ana_psource.h.

So, is it feasible that only setting the salt tracer on?

Yours
WangQian

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kate
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Re: River bottom salinity too high

#4 Post by kate » Fri Aug 03, 2018 4:31 am

Yes, ROMS will let you do that. The numerics will not be stable.

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m.hadfield
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Re: River bottom salinity too high

#5 Post by m.hadfield » Sun Aug 05, 2018 10:41 pm

I don't know if this is relevant here, but even with a well-specified river, ROMS tends to generate an estuarine flow (outflow at the surface, inflow at the bottom) at the grid cell the river enters. The advection scheme can then generate hypersaline water at the bottom, which tends to form a plume flowing down the shelf in the bottom layer. There are various things you can do to minimise this: the main one is to use a river mass flow profile (Vshape) that is largest near the surface and zero at the bottom.

And to second Kate, it is highly recommended to specify all tracers in the river flow. If you don't do this, you get the worst sort of instability: one that lies dormant waiting to crop up at the time of maximum inconvenience.

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jivica
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Re: River bottom salinity too high

#6 Post by jivica » Mon Aug 06, 2018 4:50 am

Adding my 2c to the topic;

I am running "many rivers scenario" without specifying temperature (only salinity) of the river sources and all is working fine (this option is using ambient ocean temperature for river sources as I don't know exactly temperature and it is shallow and really similar to the ocean values anyway).

As Mark wrote, you have to be careful about specifying vertical flux and usually we define strong inflow at the surface using river_Vshape. If you can upload your river forcing file then we could check and possibly give you advice if it is wrong. On the other hand are you sure you have correct river_Eposition and river_Xposition defined? Long time ago Rich Signell made map_rivers.m that is plotting your grid and river forcing file so you can check it quickly.


Cheers
Ivica

WANGQIAN
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Location: Second Institute of Oceanography

Re: River bottom salinity too high

#7 Post by WANGQIAN » Mon Aug 06, 2018 9:00 am

Thank you kate, mark and Ivica,
I find some error with my river forcing file. When I do my python script, some transport data is positive for outflow :oops: . Now I fix them, the model is stable.
And I only use salt trace with all Vshape equal.
If the model gets unstable, I will adjust them.
Thank you again! :D

Yours
WangQian

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m.hadfield
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Re: River bottom salinity too high

#8 Post by m.hadfield » Tue Aug 07, 2018 10:25 am

I am running "many rivers scenario" without specifying temperature (only salinity) of the river sources and all is working fine
If you're lucky it will continue to do so. :wink:

dullman
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Re: River bottom salinity too high

#9 Post by dullman » Tue Aug 07, 2018 7:23 pm

I have also encountered this problem of hypersaline water at depth near river inflow points. In addition to the suggestion that the inflow be specified (using Vshape) to be stronger at the surface, I have also found that making the water depth uniform in a small area around the inflow point helps to alleviate this problem.

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jivica
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Re: River bottom salinity too high

#10 Post by jivica » Wed Aug 08, 2018 4:42 am

Actually the best option would be to dig a uniform depth/width channel inland (a few pixels should be enough) and have mixing processes happening "over the land", so once entering the ocean it is as should be.

Cheers,
Ivica

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