Parallel Grid Manipulations in Earth

We introduce the parallel grid manipulations needed in the Earth Science applications currently being implemented at the Data Assimilation OOce (DAO) of the National Aeronautics and Space Administration (NASA). Due to real-time constraints the DAO software must run eeciently on parallel computers. Numerous grids, structured and unstructured are employed in the software. The DAO has implemented the PILGRIM library to support multiple grids and the various grid transformations between them, e.g., interpolations , rotations, prolongations and restrictions. It allows grids to be distributed over an array of processing elements (PEs) and manipulated with high parallel eeciency. The design of PILGRIM closely follows the DAO's requirements, but it can support other applications which employ certain types of grids. New grid deenitions can be written to support still others. Results illustrate that PILGRIM can solve grid manipulation problems eeciently on parallel platforms such as the Cray T3E.