[MITgcm-support] vertical velocities in high-res runs

[Andreas Klocker]

Hi everyone,

I've got a little problem with vertical velocities in I high-res run which I don't understand and I have no idea how to get rid of that problem.

The model is a channel with realistic topography, 1/20 deg resolution, 150 vertical layers, see below data file for more info.

The problem: As you can see in the attached figure of the vertical velocity I always get two lines (which not quite follow isopycnals) which have very strong grid-scale vertical velocities along them which do not make sense. I tried both advection scheme 7 and 33 and it doesn't make much of a difference. When I add more Smagorinsky visc. the whole velocity filed gets much smoother and less energetic but the problem of the grid-scale noise doesn't change. If I use KPP it produces large vertical diff. in those regions but the problem doesn't go away...I'm not sure what else to try...

Has anyone got an idea what could cause that problem and how to solve it?

cheers,
Andreas

# Continuous equation parameters
  &PARM01
  tRef               = 150*5.0,
  sRef               = 150*34.5,
  viscAr= 5.6614e-04,
  diffKrT=1.e-5,
  diffKrS=1.e-5,
  no_slip_sides=.FALSE.,
  no_slip_bottom=.TRUE.,
  rhonil=1027.5,
  rhoConstFresh=999.8,
  eosType='JMD95Z',
# hFacMinDr=50.,
# hFacMin=0.5,
  hFacInf=0.01,
  hFacSup=2.,
  select_rStar=2,
  nonlinFreeSurf=4,
  implicitDiffusion=.TRUE.,
  implicitViscosity=.TRUE.,
# ivdc_kappa=100.,
  viscC4Leith=2.,
  viscC4Leithd=2.,
  viscC2Leith=1.5,
  viscC2Leithd=1.5,
  viscA4GridMax=0.5,
  viscC2Smag=1.5,
# viscA4=2.0E8,
# viscAhD=60,
  useAreaViscLength=.TRUE.,
  sideDragFactor=0.,
# highOrderVorticity  = .TRUE.,
  useAbsVorticity=.TRUE.,
  selectVortScheme=2,
  selectKEscheme=3,
  bottomDragQuadratic = 0.0025,
  tempAdvScheme=7,
  saltAdvScheme=7,
  StaggerTimeStep=.TRUE.,
  multiDimAdvection=.TRUE.,
  vectorInvariantMomentum=.TRUE.,
  implicitFreeSurface=.TRUE.,
  exactConserv=.TRUE.,
# debuglevel=4,
  convertFW2Salt=-1
  useRealFreshWaterFlux=.TRUE.,
  useSingleCPUio=.TRUE.,
  globalFiles=.TRUE.,
  allowFreezing=.TRUE.,
# useJamartWetPoints=.TRUE.,
  &

-- 
===============================================
Dr. Andreas Klocker
Research Fellow

Center of Excellence for Climate System Science
&
Geophysical Fluid Dynamics Group
Research School of Earth Sciences
Room J7.221, Jaeger 7 Building
The Australian National University
Canberra ACT 0200 Australia

T:     +61 2 6125 0920
M:     +61 437 870 182
W:     http://web.mit.edu/aklocker/www/
skype: andiklocker
===============================================

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