AMM

Abstract

Approximations on polygonal grids, such as cube sphere or icosahedral require a slightly irregular grid, as for high resolution no uniform polygonal cover by cells is possible. For variable resolution sudden refinement is considered not possible by some authors and a gradual change of resolution is preferred,such as with the new MPAS model of NCAR. It will be shown that such problems can be traced back to a decrease of approximation order to 1 in points where the resolution is irregular. Examples will be given to show that a jump of resolution is possible without problems when care is taken that in such points an approximation order 2 or 3 is maintained.