Extending scalability of the community atmosphere model

Abstract

The Community Atmosphere Model (CAM) is the atmosphere component of the Community Climate System Model (CCSM), and is the largest consumer of computing resources in typical CCSM simulations. The parallel implementation of the Community Atmosphere Model (CAM) employs a number of different domain decompositions. Currently, each decomposition must utilize the same number of MPI processes, limiting the scalability of CAM to that of the least scalable decomposition. This limitation becomes unacceptably restrictive when including additional physical processes such as atmospheric chemistry or cloud-resolving physics. This paper reports on current efforts to improve CAM scalability by allowing the number of active MPI processes to vary between domain decompositions.