[RegCNET] CFL>1 violation error

[Chao Tang]

Dear all,


I got CFL>1 euro bellow, when running RegCM-4.5.0:

===================================================

 Initial date of the global simulation: 2004-10-02 00:00:00 UTC
 Initial date of this run             : 2004-10-02 00:00:00 UTC
 Final date of this run               : 2005-07-01 00:00:00 UTC
 Total simulation lenght              :         6528  hours
 Timestep in seconds =    2.000000
 Reading Domain file : input/LaReunion_DOMAIN000.nc
 Setting IPCC scenario to A1B

…

Boundary Pameterizations
  Nudge value high range     :  3.000000
  Nudge value medium range   :  2.000000
  Nudge value low range      :  1.000000
 Model Timestep Pameterizations
  time step for dynamical model in seconds :     2.000000
  time step for surface   model in seconds :   600.000000
  time step for cumulus   model in seconds :   300.000000
  time step for radiation model in minutes :    30.000000
  time step for emission  model in hours   :     6.000000
 Domain grid parameters:
  Map Projection        : LAMCON
  Dot Grid Full Extent  :  260x 160x 18
  Model Top Pressure    :    5.000000 cb
  Model Grid Spacing    :    3.000000 km
  Grid Center Latitude  :  -20.800000 deg
  Grid Center longitude :   56.300000 deg
  True Latitude 1       :   30.000000 deg
  True Latitude 2       :   60.000000 deg

…


$$  no. of points with active convection =    7557
 SEARCH BC data for 2004101400, ktau =   507600
 READY  BC from       2004101318  to   2004101400
 ATM variables written at 2004-10-13 18:00:00 UTC
 SRF variables written at 2004-10-13 18:00:00 UTC
 RAD variables written at 2004-10-13 18:00:00 UTC
 $$$ 2004-10-13 18:00:00 UTC, ktau   =           507600
 $$$ max value of CFL =  0.26060E-01
 $$$  no. of points with active convection =    5389
CFL>1: CFL =       1.0019 W =    -187.4752  I =    49  J =    91  K =    14
CFL>1: CFL =       1.0242 W =    -144.4658  I =    49  J =    91  K =    15
 -------------- FATAL CALLED ---------------
  Fatal in file: mod_sound.F90 at line:      686
 CFL violation
 -------------------------------------------
 Abort called by computing node           34 at 2016-09-21 14:37:20.171 +0200
—————————————————————————————————————


As shown above:
1. ds=3km, dt=2s, domain=260*160*18 grid;
2. the simulation starts from 2004-10-02, and stopped around 2004-10-13.




Questions:
1, For CFL in RegCM, I/J are number of grid, K is the vertical level ?
2, what the meaning of W ?
3, How this 3D CFL calculated in RegCM-4.5.0 ?
4, Any idea to fix this error ?


Thanks a lot in advance .


Cheers,
Chao TANG

University of La Reunion, France.






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