living-with-roms.pdf - Living with ROMS Deepak Cherian...

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Living with ROMS Deepak Cherian January 14, 2016 Contents Contents 1 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Misc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3 Numerical artifacts / noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4 GLS turbulence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5 Calculating budgets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6 Output variables to file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7 Time stepping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8 Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 9 CPP Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 10 Useful code files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 11 Vertical Mode Splitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 12 Pressure Gradient Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 13 Model Spinup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1
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CONTENTS 2 14 Nudging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 15 Open Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 16 Rho0 and R0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 17 Horizontal Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 18 Lagrangian Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 19 Passive Tracers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 20 NETCDF-4 output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 References 25 1 Introduction Shchepetkin and McWilliams ( 2009 ) has a good overview of ROMS design philosophy. a dsd lo 2 Misc Advection schemes have an impact on instability growth rates. See Durski & Allen (2005). Numerical mixing? Use ncgen -b *.cdl to create a netcdf file based on trunk/Data/ROMS/CDL/*.cdl . Nonlinear/prsgrd.F describes which header file contains code for each pressure gradient CPP option. ANANAME (*) - gives path to analytical header files used (search for ANANAME in analytical.f90 ). Also present in stdout output. Use NINFO=1 to force ROMS to check for bad values of variables at every timestep. This forces it to write a restart record when it blows up. If it can’t find libraries, you might have to add something to LD_LIBRARY_PATH . The command ldd oceanM will tell you what libraries it is linked to. In FORTRAN files, xl(ng) and el(ng) will give you domain extents. You will need to add a include mod_grid statement at the top of the file.
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CONTENTS 3 Hz = diff(z_w,1,3) in MATLAB. See ROMS/Nonlinear/set depth.F Line 239. Hz is the height of the grid cell. Apparently, ROMS applies no-slip boundary conditions to masked areas. This is hardcoded in. See Utility/metrics.F and scylla = 12 × 10 4 points per tile with 200 points in x-dir. Interpolation with ROMS grids in MATLAB is apparently tricky. See . org/projects/src/ticket/565 . ANA DRAG requires UV DRAG GRID . Actually, UV DRAG GRID says that you want spatially varying drag coefficients. Then ANA DRAG says you want it specified analytically and not read from netCDF file. 3 Numerical artifacts / noise 3.1 Internal waves Mostly from Batteen and Han ( 1981 ), 1. Accurate dispersion of IGWs required to simulate geostrophic adjustment. 2. Spatial averaging to compute the Coriolis force in C-grids introduces computational noise and distorts the dispersion relation. 3. Two grid point internal waves in the C-scheme, behave like gravity waves in a non-rotating fluid, due to the averaging of the Coriolis force. Because of the non-dispersive characteristic of the gravity waves, these waves do not disperse the energy, resulting in the two grid noise pattern. 3.2 OBC noise Sponge layers work - need to be careful about reflections. Comparing a periodic run with an OBC run helps identify if the open boundary is really the source of noise.
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CONTENTS 4 3.3 2dx noise For viscosity parameter choices, see section 17.1 .
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  • Summer '17
  • idk
  • Fluid Dynamics, Boundary value problem, McWilliams, Boundary conditions

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