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.