A New Synoptic Scale Resolving Global Climate Simulation using the Community Earth System Model
High-resolution global climate modeling holds the promise of capturing planetary-scale climate modes and small-scale (regional and sometimes extreme) features simultaneously, including their mutual interaction. This paper discusses a new state-of-the-art high-resolution Community Earth System Model (CESM) simulation that was performed with these goals in mind. The atmospheric component was at 0.25° grid spacing, and ocean component at 0.1°. One hundred years of “present-day” simulation were completed. Major results were that annual mean sea surface temperature (SST) in the equatorial Pacific and El-Niño Southern Oscillation variability were well simulated compared to standard resolution models. Tropical and southern Atlantic SST also had much reduced bias compared to previous versions of the model. In addition, the high resolution of the model enabled small-scale features of the climate system to be represented, such as air-sea interaction over ocean frontal zones, mesoscale systems generated by the Rockies, and Tropical Cyclones. Associated single component runs and standard resolution coupled runs are used to help attribute the strengths and weaknesses of the fully coupled run. The high-resolution run employed 23,404 cores, costing 250 thousand processor-hours per simulated year and made about two simulated years per day on the NCAR-Wyoming supercomputer “Yellowstone.”
Funding for the research on this project came from the Department of Energy Office of Biological and Environmental Research, via the Scientific Discovery through Advanced Computing (SCIDAC) project SC0006743, and we also acknowledge the National Science Foundation and the NCAR “Accelerated Scientific Discovery” computer allocation for extensive use of Yellowstone at the NCAR-Wyoming supercomputer center. Dave Hart of the Computational and Information Systems Lab (CISL) gave excellent support for the project, and the CISL group also provided assistance for performing large jobs on the then-new Yellowstone supercomputer. Thank you to Andy Mai for performing part of the simulation, John Truesdale for analysis of Tropical Cyclones, Jim Edwards and Tony Craig for advise on running CESM at high resolution, and Mark Taylor for advice on running the Spectral Element version of CAM. Rich Neale, Andrew Gettelmann, Jack Chen, and Aneesh Subramanian are thanked for providing comments on the Intraseasonal variability section. Lisan Yu and Xiangze Jin kindly provided access to 0.25° OAFLUX data. James Booth shared analysis of the ERA-Interim storm tracks. Two anonymous reviewers are thanked for their constructive criticism which helped strengthen the paper. The model simulation data from CESM-H are available to the public, at the Earth System Grid, on the webpage http://www.earthsystemgrid.org/. The animations of MCS over the Rockies and of latent heat flux over SST, both using hourly data, can be found on YouTube at https://www.youtube.com/playlist?list=PL5BdpEleiG4Boo-JCGr_34WmnNf9tt4wn.