The primary function of the CCSM coupler is to coordinate the execution of, and interactions between, the various component models which comprise a single configuration of the CCSM. Critical functionality in the coupler includes synchronization of the time integration of the coupled system, managing inter-model data communication, conservatively mapping data between the various model grids, and computing certain interfacial fluxes between components. The coupler must perform these functions whenever and wherever performance, software engineering, or scientific requirements dictate. The design and implementation of CCSM coupler version 6, the ``next generation'' coupler, will represent significant advances over previous coupler implementations, in particular, the CCSM and PCM couplers.
The primary motivations for creating a new coupler are (1) to create a single coupler that will replace the existing PCM and CCSM couplers, thus unifying the PCM and CCSM modeling efforts, and (2) to support the creation of a performance-portable CCSM, one which can execute efficiently on a range of platforms, in a variety of configurations. Thus, the coupler requirements should clearly address the goal of delivering performance portability across scalable parallel supercomputers, commodity clusters, shared memory multiprocessors, and vector supercomputers.
Continuing the naming sequence familiar to the CCSM community, this coupler is called "cpl6", or "the CCSM coupler, version six." Among developers, cpl6 is also known as the "next generation coupler" or "ngc."