Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 6 2004 10.5194/acpd-4-7139-2004 http://www.atmos-chem-phys-discuss.net/4/7139/2004/ http://www.atmos-chem-phys-discuss.net/4/7139/2004/acpd-4-7139-2004.html http://www.atmos-chem-phys-discuss.net/4/7139/2004/acpd-4-7139-2004.pdf 7139 7166 2004-11-04 Technical Note: The Modular Earth Submodel System (MESSy) – a new approach towards Earth System Modeling P. Jöckel R. Sander J. Lelieveld Max Planck Institute for Chemistry, P.O. Box 3060, 55020 Mainz, Germany Generally, the typical approach towards Earth System Modeling has been to couple existing models of different domains (land, ocean, atmosphere, ...) offline, using output files of one model to provide input for the other. However, for a detailed study of the interactions and feedbacks between chemical, physical, and biological processes, it is necessary to perform the coupling online. One strategy is to link the existing domain-specific models with a universal coupler. In many cases, however, a much simpler approach is more feasible. To achieve the online coupling, we have developed the Modular Earth Submodel System (MESSy). Data are exchanged between a and several within one comprehensive model system. MESSy includes a generalized interface structure for the standardized control of the and their interconnections. The internal complexity of the is controllable in a transparent and user friendly way. This provides remarkable new possibilities to study feedback mechanisms (by two-way coupling), e.g., by applying MESSy to a general circulation model (GCM).