2.6 RRTMG-P: An Updated and Standardized Radiative Transfer Package for Earth System Applications on High Performance Computing Systems

Pincus, Robert, University of Colorado, John Dennis, Brian Eaton, Youngsung Kim, National Center for Atmospheric Research, and John Michalakes, University Corporation for Atmospheric Research/Cooperative Programs for the Advancement of Earth System Sciences

RRTMG-P is a new, fully modernized implementation of AER's highly successful Rapid Radiative Transfer Model. The P standing for parallel. For the past two decades, RRTMG has been widely successfully adopted by a host of institutions (ECMWF, NCEP, NCAR, NASA, NRL and many others) for efficient simulation of longwave and shortwave radiation in numerous weather and climate applications, including WRF. Now, after almost twenty years, this efficient approximation to the Line-by-Line Radiative Transfer Model (LBLRTM) has become less suited to exploit vector performance on new generations of processors (GPU and MIC). Also a victim of its success, the software has diverged over multiple separately developed and maintained versions. RRTMG-P has been completely redesigned and its software rewritten using an object-oriented design under funding by the Air-Ocean-Land-Ice Global Coupled Prediction project of the multi-agency Earth System Prediction Capability (ESPC) program . Performance optimization on advanced architectures is ongoing. We will present an overview of the project, RRTMG-P's innovative unified design, and issues and results relating to optimizing HPC performance, and status of readiness for wider community adoption.