A new synoptic scale resolving global climate simulation using the Community Earth System Model

TLDR

High‑resolution global climate modeling can simultaneously capture planetary‑scale modes and small‑scale regional or extreme features and their interactions. The paper presents a new state‑of‑the‑art high‑resolution Community Earth System Model simulation designed to achieve these capabilities. The simulation used a 0.25° atmospheric grid and 0.1° ocean grid over 100 present‑day years, with single‑component and standard‑resolution coupled runs for comparison, and ran on 23,404 cores costing 250 k processor‑hours per simulated year, producing about two simulated years per day on Yellowstone. The high‑resolution run accurately reproduced equatorial Pacific SST and ENSO variability, reduced tropical and southern Atlantic SST bias, and resolved small‑scale features such as air‑sea interaction over frontal zones, mesoscale systems from the Rockies, and tropical cyclones.

Abstract

Abstract 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.”