Quick question for vertical mixing

[seashellingolds]

Hi All

In ROMS 3.0 I used before, the variable Akt is dimensioned by total tracer number NT, so I can simply use Akt_bak for TS from stardard input and for bio tracers from bio input file or I can redefine them using ANA_VMIX
Now I am using new ROMS, Akt has dimension of NAT which usually is 2. It seems by default bio Akt will use the same as salinity Akt. My question is how does AKT_BAK in the stardard bio input work?
If I want to change bio tracer Akt into my own form, how can I do that?

Thanks in advance

[seashellingolds]

Maybe I need extend the length of Akt from NAT to NT, so I might be free to define Akt for bio tracers
But I guess this is not the original intention of bio model design

[kate]

Do what you need to do, but do you really want NBT new values of AKt?

[seashellingolds]

Actually the answer can be no. I am just starting to learn bio model in ROMS and doing my class project. I think it is better to set bio Akt the same as salinity (means do nothing).

I realized new ROMS is designed to seperate bio model part, which really simplify the work of adding a new model. That is why I choose this version to do my project. I dont know if this is the reason to reduce the length of Akt (but Akt_bak is left unchanged). It seems Akt_bak in the stardard bio input file is not useful

Therefore, I ask just for curiosity Could some applications need such modification (use bio Akt different from salt)? I have no enough knowledge on this

[hetland]

The mixing value for salinity is used for all passive tracers, as this represents the mixing of actual molecules. Heat can be transferred without moving molecules around.

[arango]

Direct measurement or parameterization of vertical mixing in the ocean is very difficult. We can satisfactorily parameterize vertical mixing in the open ocean. However, this becomes very complicated as we approach coast regions and estuaries. We do well parameterizing vertical mixing for temperature and salinity because we know the dynamical processes associated with interior mixing, and the surface and bottom boundary conditions. At the surface, we have surface heat flux and surface freshwater (E-P) flux. Actually, the E-P flux is very problematic in ocean modeling. It is not a well known quantity!!! We hope that the new surface salinity measurements from satellites (Aquarius, SMOS) will help us to constraint this flux better.

For other passive tracers (biology, chemical, sediment) we know very little about vertical mixing. We even don't know how to parameterize it. So we assume that whatever the vertical parameterization of vertical mixing, we use the values of salinity for other passive tracers. For example, how do you parameterize vertical mixing for phytoplankton and zooplankton biomass concentration? Ecosystem modelers have bigger problems modeling the biomass that worrying about its vertical mixing.

[seashellingolds]

well, I see, many thanks. It seems we have no pre-knowledge about that and therefore no better choice.