The WRF–3DVAR system is based on the MM5–3DVAR
system (Barker et al., 2004); further developments and
progress can be found in Skamarock et al. (2008). The WRF–
3DVAR system is based on the multivariate incremental formulation
(Courtier et al., 1994), where the preconditioned
control variables are stream function , velocity potential ,