  The linearization of the meteorological equations around a specified
reference state, usually applied in NWP to define the linear system of
constant-coefficients semi-implicit schemes, is outlined as an unnecessarily
restrictive approach which may be detrimental in terms of stability. It is
shown theoretically that an increased robustness can sometimes be obtained by
choosing the reference linear system in a wider set of possibilities. The
potential benefits of this new approach are illustrated in two simple examples.
The advantage in robustness is not obtained at the price of an increased error
or complexity.
