Performance of a Parallel Global Atmospheric Chemical Tracer Model

As partof a NASA HPCC Grand Challenge project, we are designing and implementing a parallel atmospheric chemical tracer model that will be suitable for use in global simulations. To accomplish this goal, our starting point has been an atmospheric pollution model that was originally used to study pollution in the Los Angeles Basin. The model includes gas-phase and aqueous-phase chemistry, radiation, aerosol physics, advection, convection, deposition, visibility and emissions. The potential bottlenecks in the model for parallel implementation are the compute-intensiveODE solving phase with load balancing problems,and the communication-intensive-advection phase. We describe the implementation and performance results on a variety of platforms,with emphasis on a detailed performance model we developed to predict performance, identify bottlenecks, guide our implementation, assess scalability, and evaluate architectures. An atmospheric chemical tracer model such as the one we describe in this paper will be one component of a larger Earth Systems Model (ESM), being developed under the direction of C. R. Mechoso of UCLA, incorporating atmospheric dynamics, atmospheric physics, ocean dynamics, and a database and visualization system.