Instability of Frontal Waves and Upper Level Frontogenesis

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Drs. Mechoso and Arakawa will continue their two primary research thrusts on fronts. First, they are investigating processes which lead to frontal formation and the generation of unstable secondary waves on fronts, particularly in the middle and upper troposphere. Second, they are developing new numerical methods suitable for the study of frontal phenomena. Previous work by the investigators now leads to the specific consideration of several topics: (1) the comparative advantages and disadvantages of models which use relative pressure (.) as the vertical coordinate and those which use potential temperature (>); (2) the origin and evolution of small-scale disturbances on fronts; (3) the role of diabatic processes in frontogenesis; and (4) the development of primitive-equation models with a vertical coordinate that gradually changes from . at the surface to > at upper levels. Under their previous grant, the principal investigators made considerable progress in their work on the development of large scale models capable of resolving frontogenetic processes. They have also succeeded in addressing some of the fundamental questions about these processes. Their research ultimately will contribute to the improvement of operational weather forecast models.