Regional Modeling: A Theoretical Discussion
Andrew Staniforth
Recherche en prévision numérique
2121 Route Transcanadienne, porte 500
Dorval, Québec
CANADA H9P 1J3
SUMMARY
The goal of regional modeling is to make a detailed forecast for a given
limited area of interest by focusion resolution over it and the immediate
vicinity. As a consequence, the period of validity is necessarily more
restricted than would otherwise be the case, and this is the price that
must be paid for locally-enhanced resolution. The principal attributes
of the non-interactive and interactive strategies for regional modeling
are described. For the non-interactive strategy, particular enphasis is
placed on the importance, difficulty, and impact, of well-posedness for
open-domain problems. A methodology is given for estimating the size of
numerical buffer zones requiered to obtain a forecast uncontaminated by
the inward propagation of inaccurately-specified lateral boundary conditions.
The interactive strategy addresses the well-posedness issue of (non-interactive)
limited-area models. A computational overhead is incurred but this can
be reduced through the use of variable resolution. It is argued that regardless
of the preferred regional modeling strategy, experiments should be undertaken
to today's regional models under carefully-controled conditions, to reflect
the significant reduction over the past two decades of other sources of
error.