set lat|lon|lev|time|ens val1 <val2>
This set command sets one dimension of the dimension environment using world coordinates.
When you enter dimensions in grid coordinates, they are always converted to world coordinates. This conversion requires some knowledge of what scaling is in use for grid to world conversions. The scaling that is used in all cases (except one) is the scaling of the DEFAULT FILE. The exception is when you supply a dimension expression within a variable specification, which will be covered later.
set lon -180 0(sets longitude to vary from 180W to 0).
set lat 0 90(sets latitude to vary from the equator to 90N)
set lev 500(sets the level to 500mb - a fixed dimension)
set ens cntrl(sets the ensemble to cntrl)