In my case I have to run model for a week to get to steady state with “HPGE” currents that are not changing any more. After smoothing you get new bathy, run the same case again and compute magnitude again, do that in a iterative way until you are happy. You want to smooth only there where you have big errors from HPGE, and keep as close as possible to real bathy. using magnitude of velocity) and create weight factor for smoothing, big magnitude big weight. Usually look at the bottom, where pressure builds up.Ģ) I identify those regions (i.e. In that way you can see what is the effect of “bad bathymetry and big rx1” and where it is introducing artificial currents because of HPGE. However we are not on z grid and there is a sigma slope so you will have effects of HPGE, which are direct consequence of “bad” rx1. In that way if you start your simulation WITHOUT any forcing! the ocean should stay (not exactly, diffusion etc, but lets pretend it does, with big confidence) in stable state, you have only vertically stable stratified density, not producing any velocity (because there are no density gradients). In other words, create ana vertical profile for temp and salt in a similar way as is done for many examples in ana_initial.h. Why/How do we smooth the bathy in ROMS? I quote a very insightful post from the ROMS forum here:ġ) compute vertically stable! profile of temp and salt for the domain you are running, horizontally homogeneous!, hence not producing any density gradients. Note that the deepest bathy has been cut off at 3000 meter: step4_LP_smooth_bath_200219.mīathymetry Change After LP Optimization. For other version, remember to download the file named as lp_solve_x.x.x.x_exe_u圆4.tar.gz. Note the lp_solve command line tool need to be installed at frist. There is a toolkit from IRB in Croatia LP Bathymetry, providing several ways to deal with the problem. step3_OPTIONAL_prim_process_roms_bath_200219.nclĢ.3 Smooth the bathemetry to satisfy the rx threshold, using the LP method. Meanwhile, we restricted the deepest bathy to 3000 m, as we do not concern the deep sea process in this relative short simulation. How to justify “too shallow”? In this case, we have a strong typhoon, using 10 s dtime in ROMS, the 10-m shallowest bathy works fine. This is quite important as the vertical velocity can easily violate the CFL condition if the shallowest water near the coast is too shallow. Of note is that here we also set the minimum bathy to 10 m. This is optional, as the following LP method is quite effective in optimizing the bathy. step2_ETOPO_bath_to_roms_200219.nclĢ.2 Preliminary process the bathy using 9-point smooth. Here we use a simple neighboring method to fill the h in each grid. įinal Domain Configuration (Outer and white inner box for WRF, and black dashed box for ROMS):Ģ.1 Use ETOPO bathymetry data to fill the h in the generated file roms_grid.nc. ! variables have a computational J-range of. ! input, Mm=eta_rho-2 where "eta_rho" is the NetCDF file ! Mm Number of INTERIOR grid RHO-points in the ETA-direction for ! variables have a computational I-range of. ! input, Lm=xi_rho-2 where "xi_rho" is the NetCDF file ! Lm Number of INTERIOR grid RHO-points in the XI-direction for Meanwhile, we need to be careful to fit the condition in Lm and Mm: The underlying cause of unstable integration is still from the bathymetry. I even tried Computer Vision algorithm to label the connected components and then remove the elements. There is an urban legend that all islands with sizes smaller than 4 px need to be removed to ensure the smooth run. For example, in our case, we need to set the ROMS in around 2.2 km spatial resolution and 900圆00 size, so I generate a geo_em file with 3 km and 1000x1000 size first.ġ.2 Generate ROMS grid system by geo_em from WRF-WPS. Now we form the ROMS grid system using WPS generated geo_em data.ġ.1 Use WPS to generate a geo_em file which is equal or larger compared to your aim ROMS domain. I skipped the WPS procedure for building WRF grid system. While buiding up the coupling framework over the GBA need more efforts. The Sandy (2012) case can be smoothly repeated by following the instructions on the manual. Here we archive the process in building the coupling framework for simulating Mangkhut (2018). Change the maximum current speed limitĪfter Repeating Sandy (2012), we finally come to start to build the coupling framework over the Guangdong-Hong Kong-Macao Greater Bay Area (GBA).
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