Block-structured Adaptive Meshes and Reduced Grids for Atmospheric General Circulation Models

Adaptive Mesh Refinement (AMR) techniques offer a flexible framework for future variable-resolution climate and weather models since they can focus their computational mesh on certain geographical areas or atmospheric events. The high-resolution domains are kept at a minimum and can be individually tailored towards user-selected features or regions of interest. In addition, adaptive meshes can be used to coarsen a latitude-longitude grid in polar regions. This allows for so-called reduced grid setups. A spherical, block-structured adaptive grid technique is applied to a revised version of the Lin-Rood Finite Volume dynamical core for weather and climate research. This hydrostatic dynamics package is based on a conservative and monotonic finite-volume dis-cretization in flux form with vertically floating Lagrangian layers. The adaptive dynamical core is built upon a flexible latitude-longitude computational grid and can be run in two model configurations: the full 3D model on the sphere and its corresponding single-level shallow water version. In this paper the discussion is focused on static mesh adaptations and reduced grids. The shallow water setup serves as an ideal testbed and allows the use of shallow water test cases like the advection of a cosine bell, moving vortices, a steady-state flow, the Rossby-Haurwitz wave or cross-polar flows. It is shown that reduced grid configu-rations are viable candidates for pure advection applications but should be used moderately in nonlinear simulations. In addition, it is demonstrated that static grid adaptations in 3D model experiments can be successfully used to resolve baroclinic waves in the storm-track region. Global error analyses of the adaptive model simulations are presented