clipping

[fereshteh]

hi all user
i am trying to create my real bathymetry by seagrid. my domain contains land and sea. minimum depth in my coarse sea is 1 m. i want to know that minimum clipping depth is just a considered depth that user should change bathymetry values less than it to that, that is because i can't find specific location for setting it ? if there is such location, please tell.
also would you please tell me what is the criterion for determining its value?
thanks so mush
fereshte

[kate]

Bathymetry clipping happens outside ROMS, in whatever tools you use to make the grid. What value to pick? I usually aim for 10 m, but sometimes have to go deeper to satisfy the rx0 constraints. Another consideration is that without WET_DRY defined, you don't want your water depths going negative. How big are your tides? Maybe you want WET_DRY defined to handle shallow areas with tides. Still, keeping rx0 small enough gets harder as you let hmin get small.

[fereshteh]

dear kate
thanks so much for your reply. it help me
i found that minimum clipping depth is idem hmin to specific bathymetry lower limit.
in my domain (Caspian sea) there is not tide.
sincerely yours
fereshte

[fereshteh]

dear arango
in above you say that you usually choose 10 m as minimum depth. so it seems that Roms model has not capability for nearshore modeling? Is not it.
What is your idea?
Thanks
fereshte

[arango]

You have to think about your question. ROMS is a terrain-following coordinates model. That is, the vertical grid positions depends on the bathymetry h. If h=0, how you can fit N vertical levels with thicknesses Hz greater than zero? The sum of all vertical level thicknesses must be greater than zero to solve the governing equations in a computer model (mathematics and physics) that represents your application grid. If h is very small, the vertical time step will be a limiter in your simulation and you will have to take ridiculously small time-steps.

It seems to me that you need consult with someone at your institution that have experience with numerical modeling. Numerical models are an approximation and we cannot get every geographical and topographical feature in our domains. I saw your grid in previous posts. You do not need to model the beach. So forget about wetting and drying for now. In modeling, we start simple and then add complexity. This is what ROMS experts will do. Ocean Modeling has to be done in stages and always takes time, even for the experts.

[fereshteh]

Dear arango
i will use your guidance
thanks