1 Development of the Simple Coupler “Scup ” for Earth System Modeling

We have developed a simple general-purpose coupler “Scup ” (Simple coupler) which is usable in earth system modeling with flexible coupling among component models, such as atmosphere and ocean general circulation models and chemical transport models. Scup provides sufficient functions required for efficient development of the earth system model at Meteorological Research Institute (MRI), and its fundamental design is also applicable for other earth system models. Each process of the component models communicates with each other directly by calling the Scup library, which is necessary for efficiently exchanging a large amount of grid data among the processes of the component models. Scup supports grid transformation for three-dimensional data in addition to that for two-dimensional data with accurate local and global conservation, which is necessary for coupling component models with different coordinates or grids. Simplicity and easiness to use are the strong points of Scup. All the source 2 code of Scup is described in Fortran and can be compiled on various platforms with a Fortran 95 compiler and MPI (Message Passive Interface) library, which contributes to good portability of Scup. 1