Spatially Varying Bottom Roughness

[richard.schmalz]

Hi....I am trying to add into ROMS a spatially varying bottom roughness, Zo. The approach is to develop this as a field similar to bathymetry within the grid generation procedure and include a field called zor at the model RHO points within the grid netCDF file. I have modified the following routines:

1. mod_ncparam.F
2. mod_grid.F
3. get_grid.F
4. set_vbc.F

I have entered a CPP definition of Z0_SVAR, which is only activated if UV_LOGDRAG is selected. I was wondering if I was missing any other routines to modify. My plan is to test the option with a constant Z0 field to see that I get the same answer with UV_LOGDRAG selected only with the same constant roughness value.

In my application, I also need to add sea level atmospheric pressure, and the U and V ROMS coordinate wind components to both the history and station files. I have modified def_station.F and wrt_station.F for the station netCDF file and def_his.F and wrt_his.F for the history netCDF file.
Again are there any other routines that I need to modify to accomplish this.

Thanks for your help,

Dick Schmalz

[kate]

Did you add zor to varinfo.dat? It needs a unique id to be used in get_grid during the reading of it.

Your plan to try a uniform zor and test it is good. I say try it and see what happens. That will tell you if you missed anything.

Your output sounds right. If you want to write to the averages file, there's a few more steps, storing up and averaging the new fields.

[richard.schmalz]

Thanks Kate....I have now modified the varinfo.dat file. I selected
Input/Output and would like to echo the bottom roughness field after it is read in, so I will work on that next. Thanks again....Dick

[feroda]

Hi Dick,
What does the spatially varying bottom roughness based on, varying with water depth or something else?
In addition, can you address us the reason you changing the bottom roughness height?
Thanks a lot!

[richard.schmalz]

The original focus on a spatially varying bottom roughness was to pattern it after bottom sediment maps and characteristic roughness lengths. It was felt that a more accurate representation of the bottom roughness would improve the predictability of ROMS within an esturary such as Delaware River and Bay. Roy Walters, USGS, used spatially varying bottom friction; the Delaware River and Bay were split into 7 distinct zones, each with its own bottom roughness. Please refer to the following two articles:

Walters, R.A. 1992: A study of salt transport processes in Delaware Bay, Proceedings of the 2nd International Conference on Estuarine and Coastal Modeling, ASCE,240-251.

Walters, R.A. 1993: A 3d, finite element model for coastal and estuarine circulation, Continental Shelf Research, 12, 83-102.

Recently, I have incorporated a spatially varying bottom roughness coefficient for use in the quadratic bottom friction formulation in ROMS. I am presently using this approach in trying to improve tidal simulations in Delaware River and Bay.