{title}      Implicit Normal Mode Initialization for a Global Finite-Element
             Semi-Lagrangian Shallow-Water Model,

{author}     L. Fillion, J. Cote, and M. Roch.

{corp author}Recherche en Prevision Numerique, Service de l'Environnement
             Atmospherique, 2121 Route Trans-Canadienne, Dorval, Quebec,
             Canada H9P 1J3.

{citation}   Atmosphere - Ocean ATOCDA, Vol. 30, No. 3, p 321-337, September
             1992. 8 fig, 1 tab, 27 ref.

{field&group}02B, 07C

{abstract}   Implicit normal mode initialization was applied to a global
             finite-element shallow-water model where a semi-Lagrangian
             treatment of the advection terms was used. The local time
             tendencies required by the initialization scheme were thus
             furnished by the semi-Lagrangian model itself. Since the
             initialization scheme was formulated in physical space, it
             allowed the nonlinear adjustment of the initial mass and wind
             fields at essentially the same accuracy as standard explicit
             normal mode initialization without having to rely on the
             explicit determination of the normal modes of the model. This
             property was especially useful since the spatial orientation of
             the model's grid was allowed to vary. For such a case, the usual
             separability in the longitudinal and latitudinal directions of
             the linearized dynamics is not possible if the variation of the
             Coriolis parameter is included in the analysis (as it should on
             the sphere). The use of a rotated coordinate system represents a
             new aspect for implicit normal mode initialization. Using real
             data, the implicit nonlinear normal mode initialization using
             the present semi-Lagrangian model on a uniform
             latitude-longitude grid was compared with an Eulerian global
             spectral shallow-water model. The effect of the rotation of the
             system of coordinates on the performance of the initialization
             scheme was also examined in detail. The results demonstrated
             that both schemes performed equally well at removing
             high-frequency noise in forecast integrations for their
             corresponding models and produced mass and wind field
             adjustments at the initial time that were remarkably close.
             Future directions of research should include development of the
             model and its initialization for medium-range and short-range
             forecasting. (Author's abstract)

{descriptors}*Atmospheric physics, *Global processes, *Mathematical studies,
             *Meteorology, *Model studies, *Numerical models, *Shallow water,
             Advection, British Columbia, Canada, Coriolis force, Finite
             element method, Forecasting, Lagrangian model, Mass balance,
             Wind effects.

{id number}  93-09673
{end}