An Overview of the GFDL Flexible Modeling System

V. Balaji
OAR/GFDL

This talk presents an overview of the GFDL Flexible Modeling System (FMS). The FMS is a software infrastructure for the construction of atmospheric, oceanic, and coupled climate system models. It attempts to address the need to develop high-performance kernels for the numerical algorithms underlying non-linear flow in complex fluids, while maintaining the high-level structure needed to harness component models of climate subsystems developed by independent groups of researchers. The code is portable across a wide variety of scalar and parallel computing architectures, and is designed for flexibility, modularity and extensibility. It forms the basis of current and future coupled modeling at GFDL. It has been recently benchmarked on a wide variety of high-end computing systems, and has run in production on three very different architectures: parallel vector, distributed massively-parallel and distributed shared-memory systems, as well as on scalar microprocessors. Models in production using the FMS infrastructure include a hydrostatic spectral atmosphere, a hydrostatic grid-point atmosphere, an ocean model, and land and sea ice models. Other codes using FMS, including a limited-area non-hydrostatic atmosphere model and an ocean data assimilation system, are under construction at GFDL.

The shared software for FMS includes, at the lowest level, a parallel framework for handling distribution of work among multiple processors. Upon this are built the exchange grid software layer for conservative data exchange between independent model grids, and a layer for parallel I/O. Further layers of software include a diagnostics manager for creating runtime diagnostic data sets in a variety of file formats, a time manager for model time and calendars, general utilities for file-handling and error-handling, and a uniform interface to scientific software libraries providing methods such as fast fourier transforms. Interchangeable components are designed to present a uniform interface, so that for instance, behind an ``ocean model'' interface in FMS may lie a full-fledged ocean model, a few lines of code representing a mixed layer, or merely a routine that reads in an appropriate data set, without requiring other component models to be aware which of these has been chosen in a particular model configuration. Coupled climate models in FMS are built as a single executable calling subroutines for component models for the atmosphere, ocean and so on. Component models may be on independent logically rectilinear (though possibly physically curvilinear) grids, linked by the exchange grid, and making maximal use of the shared software layers. This talk will present an overview of the structure of FMS, the standards for the construction of model components, and finally present examples of scientific results. The FMS is scheduled for public release in March 2002.

BIO - Dr. Venkatramani Balaji Born in Madras, India. Education: M.Sc (Physics) 1981, Indian Institute of Technology, Kanpur. Ph.D (Physics) 1988, Ohio State University and NCAR Advanced Study Program. Current Position: Senior Applications Analyst, SGI, on-site at GFDL since September 1997. Previous Affilications: Visiting Scientist, Princeton University; September 1996--August 1997. Project Scientist, York University, Canada; January 1991--September 1996. Visiting Fellow, Centre National de Recherches Meteorologiques, Toulouse, France; July 1988--November 1990. Post-doctoral Research Associate, Department of Geophysical Sciences, University of Chicago, Chicago, USA; November 1987--May 1988. Professional Interests: High-performance computing, parallel and vector codes for atmospheric and ocean dynamics, numerical modeling of weather and climate, small-scale atmospheric dynamics and multi-scale phenomena. Software design for scientific applications. Personal URL: http://www.gfdl.noaa.gov/~vb/

Conference Center - Paper Wednesday - 11:30 - 12:00 A.M.