/DomainDefinition

Indications in how to define a simulation domain in WRF

There are a lot of aspects to take into account when defining a domain in WRF, here are some assistance

Extension of the domain

The extension of the domain might depend on the type of experiment. Area of interest should be far away fromthe borders of the domains in order to:

1. Allow to develop the atmosphere dynamics at the selected resolution of the domain. This will ensure that features (e.g. cyclones, fronts, ...) are properly developed
2. Each domain has a given amount of grid points used as interface between fields outside domain and inner domain (in namelist.input). Dynamics within these grid points is not fully correct:

&bdy_control
 spec_bdy_width                      = 10,
 spec_zone                           = 1,
 relax_zone                          = 9,
...

See some references:

• Brisson, E., Demuzere, M., & Van Lipzig, N. P. M. (2016). Modelling strategies for performing convection-permitting climate simulations. Meteorologische Zeitschrift, 25(2), 149–163. doi: 10.1127/metz/2015/0598
• Sichan Du et al., 2025: Exploring suitable domain size for high-resolution urban rainfall simulation, doi: 10.1016/j.uclim.2025.102489

Space distortion

In order to avoid numerical instabilities is recommended that the domain does not distortions too much the real space. This information is contained in the MAPFAC_M variable. It is recommendable to have values of the variable as closest to one as possible all over the domain.

This variable shows the difference between grid size in the WRF domain and the actual size being represented. The further away MAPFAC_M is from 1., the larger the distortion is.

For example, in a Lambert-Conformal projection, MAPFAC_M is 1. at the true_lat1, true_lat2. Would be recommendable to locate these latitudes one at 1/4 of the y-size of the domain, and the other one at 3/4.

Be aware that as larger the values of MAPFAC_M get, you should reduce the time-step of integration as it is said in the rsl.error.0000 file for example:

Max map factor in domain 1 =  1.03. Scale the dt in the model accordingly.