Atmos Wiki

If you are performing multiple runs (a run involving multiple hours of model time), you only run 3d.params on your initial run.

This page will guide you through what each of the parts of the 3d.params namelist covers

0000.0 start time

This is the time from which you would like the model to initialize from. This time is independent of rampup.

'sounding' prefix name for sounding input and init output

This is the name of your sounding file. (*.sound)

98 98 77 nx,ny,nz; num nodes on coarse grid

This is the number of nodes on your domain. i.e. if you have 1 km x 1 km resolution, your grid size would be 98 km x 98 km. If you had a resolution of 2 km x 2 km, your grid size would be double the nodes. nx * dx = grid size.

3. 4 dt,ns; coarse grid step and num small steps

dt is VERY important (time step in Courant number). You MUST make sure your dt is small enough to track your updraft.

7.67 -1.75 um,vm; mean wind

Sometimes it is necessary to move the domain box to follow a thunderstorm to make sure the storm never leaves the domain. This line allows the adjustment of 'u' movement and 'v' movement.

0 0 0 bcx,bcy,bcz; bndry cond'n flags--see description below

(Please fill in)

1 upper-radiation BC on (1) or off (0)

(Please fill in)

9000. 36000. 72000. wavlen's (m) of true KDB radiation

(Please fill in)

0 flag for 2D run (if set, use ny=5 and bcy=-1)

(Please fill in)

0.0 0.0 gx0,gy0; coordinates of the SW corner of grid

(Please fill in)

1000. 1000. dx,dy; coarse grid spacing

This is where you will decide which resolution you would like. Most supercell runs take 2km x 2km x 500 km. However, feel free to use whichever you prefer.
Grid spacing is in meters. To obtain the domain size, multiply the coarse grid (98 98) by the coarse grid spacing.

250. 0 dz, stretching flag (on (1) or off (0));if on, read stretch.dat

See previous.

0 terrain type--see description below

VERY IMPORTANT! The default flag with UWCOMMAS is type 4…unless you want a mountain in your run, change this to 0. See description of terrain types below.

10000. 10000. 1000. x_scale,y_scale,z_scale; terrain parameters

(Please fill in)

10000. 10000. 00000. x_scale2,y_scale2,y_len; terrain parameters

(Please fill in)

90000. 90000. 0. x_0,y_0,z_0; terrain parameters

(Please fill in)

1 0 num bubbles and perturb'n theta; bubble params below

num bubbles is the number of bubbles in your run. These bubbles are the convective initiation for the model.
perturb'n theta is how warm the bubble starts

35000. 30000. 1500. 9000. 9000. 1500. xpos,ypos,zpos,xrad,yrad,zrad

This is the position and size of the bubble

0

(Please fill in)

0 0 0 0 0 0

(Please fill in)

0 inflow bc for scalar (0); not used

(Please fill in)

200.0 max sound speed (cs < 0 => base state)

(Please fill in)

0 compressible Boussinesq (1) or fully compressible (0)

This is just a flag for if you'd like to use an assumption of a Boussinesq fluid or if you want to assume fully compressible

0 Boussinesq hydrostatic (1) or non-hydrostatic (0)

Similar to the previous flag. This turns hydrostatic assumptions on/off

-1 displacements (0) or Boussinesq vorticity (1) or nothing (-1)

(Please fill in)

0.0e-4 Coriolis parameter

Just what it sounds like

0 noise on (1) or off (0)

Just another flag that means what it says

0.e-4 anoise; noise amplitude (fraction of reference theta)

(Please fill in)

0. cnoise; cutoff length for noise spectrum (in grid units)

(Please fill in)

0. tnoise; time at which noise is added

(Please fill in)

1 sub-gridscale mixing on (1) or off (0)

(Please fill in)

00. alowk0; vertical background damping

(Please fill in)

-1. ahighk; vertical background damping

(Please fill in)

0.21 Cm (0.21); mixing coeff

(Please fill in)

3.0 1/Pr (1.5 or 3.); inverse Prandtl num

(Please fill in)

0.20 f4damp (f4damp * .0625/(2*dt) is actual model coefficient)

(Please fill in)

95500. rayleigh damper initial hgt

(Please fill in)

.000 rayleigh damper tau

(Please fill in)

0.2 vertical implicit coef (0 to 1)

(Please fill in)

0.15 asselin time filter

(Please fill in)

0.00 non-dim divergent damper coeff (0.0)

(Please fill in)

3.0e-3 drag coeff for velocity

(Please fill in)

3.0e-3 drag coeff for heat

(Please fill in)

2.1e-3 drag coeff for moisture

(Please fill in)

30.0 outflow gravity wave speed

(Please fill in)

These next several lines are descriptors of previous flags

BCX,BCY: 0 → outflow conditions

       1 -> nested grid
      -1 -> periodic
      -2 -> symmetry conditions at 0 and L
      -3 -> symmetry conditions at 0, outflow at L
      -4 -> outflow conditions at 0, symmetry at L

BCZ : 0 → freeslip

       1 -> surface layer (not implemented)

terrain_type: 0 → no terrain;

            1 -> hat in x, h = h(x)
            2 -> hat in y  h = h(y)
            3 -> x,y hat   h = h(x,y)
            4 -> cos^4 hat in x,y  h = h(x,y)
                   elongated in y
                   separate upstream/downstream x scales