WRF ARW User's Guide - MMM - UCAR

WPS
When configuring a rotated latitude-longitude grid, the namelist parameters pole_lat,
pole_lon, and stand_lon are changed from their default values. The parameters
pole_lat and pole_lon specify the latitude and longitude of the geographic north pole
within the model’s computational grid, and stand_lon gives the rotation about the
earth’s axis. In the context of the ARW, the computational grid refers to the regular
latitude-longitude grid on which model computation is done, and on whose latitude
circles Fourier filters are applied at high latitudes; users interested in the details of this
filtering are referred to the WRF Version 3 Technical Note, and here, it suffices to note
that the computational latitude-longitude grid is always represented with computational
latitude lines running parallel to the x-axis of the model grid and computational longitude
lines running parallel to the y-axis of the grid.
If the earth’s geographic latitude-longitude grid coincides with the computational grid, a
global ARW domain shows the earth’s surface as it is normally visualized on a regular
latitude-longitude grid. If instead the geographic grid does not coincide with the model
computational grid, geographical meridians and parallels appear as complex curves. The
difference is most easily illustrated by way of example. In top half of the figure below,
the earth is shown with the geographical latitude-longitude grid coinciding with the
computational latitude-longitude grid. In the bottom half, the geographic grid (not shown)
has been rotated so that the geographic poles of the earth are no longer located at the
poles of the computational grid.
WRF-ARW V3: User’s Guide 3-11