DIY the Integrated Climate Model and its computational performance

TL;DR

This paper presents the development, optimization, and benchmarking of a DIY integrated climate model combining ECHAM5 and NEMO2.3, demonstrating high computational performance and operational capabilities on supercomputers.

Contribution

It introduces a flexible framework for building a coupled climate model with improved coding, restart features, and performance benchmarking on supercomputers.

Findings

ICM can simulate over 100 model years per day.

Successfully integrated ECHAM5 and NEMO2.3 with improved communication.

Achieved high-performance climate simulations on supercomputers.

Abstract

This article describes the software engineering framework and computation performance of a global climate system model which helps the user to understand the step-by-step technical to DIY(do it yourself) a climate model by your own. The model integrates ECHAM5 and NEMO2.3 using OASIS3 as the coupler. The program skill of the Integrated global Climate Model (ICM) is demonstrated here, including the porting of NEMO into the COSMOS framework, the organization of variable exchange, and component model communication synchronization. We describe how we successfully fixed some bugs in the component models and detail the new code and scripts that were added to ICM. In particular, an improvement of ICM's coding is that we enabled it to perform perfect restart runs, which is an important feature that was not implemented in the original version of NEMO2.3. ICM is designed as a model hybrid for both research and operational applications. Its scripts manage and utilize numerical simulations including data preparation, namelist file control, CPU allocation, job submission, job restarting, post-data combination and plotting. ICM is now successfully set up and runs at Dawning in the CMSR and the Tianhe-1A supercomputer system in the National Supercomputer Center in Tianjin, and the speed benchmark has been obtained. Results indicate that it can simulate the climate at more than 100 model years per day (maximum of 175 yrs/d), which represent a high level of performance for a fully coupled climate model. Finally, a summary of the 1500-year long-term control experiment using ICM is provided.