Abstract : The aim over three years is to advance fundamental understanding of middle atmospheric dynamics, particularly with regard to the vertical and horizontal dynamical coupling associated with planetary scale motions and their interactions with other scales. The immediate aims of the first year are to continue with high-resolution barotropic planetary wave-breaking simulations, to extend these to fully three-dimensional baroclinic simulations using the Cray X- MP/48. The approach is to build and use a sophisticated numerical modelling capability, exploiting the Global Atmospheric Modelling Project, to develop abstract theoretical concepts that are likely to lead to dynamical insight and test them in numerical experiments, and to develop new and efficient ways for scientists to interact with numerical models, exploiting modern workstation facilities. One milestone was the successful initiation of three-dimensional, high-resolution numerical simulations of breaking planetary waves, building upon the barotropic modelling work initiated earlier and still continuing. (jhd)