http://www-unix.mcs.anl.gov/mct/

From the web site:

• MCT is a set of open-source software tools for creating coupled models.
• MCT is fully parallel and can be used to couple message-passing parallel models to create a parallel coupled model.
• MCT is available as a small library and a set of Fortran90 modules.
• MCT provides model interoperability through a simple API. Two models that declare and use MCT datatypes can be coupled with a minimum of effort.
• MCT provides the following core coupling services:
  • a component model registry
  • domain decomposition descriptors
  • communications schedulers for parallel MxN? intercomponent data transfer and MxM? intracomponent data redistribution
  • a flexible and indexible (i.e., random-access) field data storage datatype
  • a time averaging and accumulation buffer datatype
  • a general spatial grid representation capable of supporting unstructured grids
  • parallel tools for intergrid interpolation implemented as matrix-vector multiplication spatial integration and averaging tools (including paired integrals to support conservative interpolation)
  • tools for merging data from multiple components for use by another component.
  • a programming model similar to that of the Message Passing Interface.