C-Coupler2: a flexible and user-friendly community coupler for model coupling and nesting

Abstract. The Chinese C-Coupler (Community Coupler) family aims primarily to develop coupled models for weather forecasting and climate simulation and prediction. It is targeted to serve various coupled models with flexibility, user-friendliness, and extensive coupling functions. C-Coupler2, the latest version, includes a series of new features in addition to those of C-Coupler1 – including a common, flexible, and user-friendly coupling configuration interface that combines a set of application programming interfaces and a set of XML-formatted configuration files; the capability of coupling within one executable or the same subset of MPI (message passing interface) processes; flexible and automatic coupling procedure generation for any subset of component models; dynamic 3-D coupling that enables convenient coupling of fields on 3-D grids with time-evolving vertical coordinate values; non-blocking data transfer; facilitation for model nesting; facilitation for increment coupling; adaptive restart capability; and finally a debugging capability. C-Coupler2 is ready for use to develop various coupled or nested models. It has passed a number of test cases involving model coupling and nesting, and with various MPI process layouts between component models, and has already been used in several real coupled models.