Submitted as: development and technical paper 09 Jun 2021

Submitted as: development and technical paper | 09 Jun 2021

Review status: this preprint is currently under review for the journal GMD.

Concurrent Calculation of Radiative Transfer in the Atmospheric Simulation in ECHAM-6.3.05p2

Mohammad Reza Heidari1, Zhaoyang Song2, Enrico Degregori3, Jörg Behrens3, and Hendryk Bockelmann3 Mohammad Reza Heidari et al.
  • 1Department of Informatics, Universität Hamburg, Hamburg, Germany
  • 2School of Atmospheric Sciences, Sun Yat-sen University, and Key Laboratory of Tropical Atmosphere–Ocean System, Ministry of Education, Zhuhai, China
  • 3German Climate Computing Center (DKRZ), Hamburg, Germany

Abstract. The scalability of the atmospheric model ECHAM6 at low resolution, as used in palaeoclimate simulations, suffers from the limited number of grid points. As a consequence, the potential of current high performance computing architectures cannot be used at full scale for such experiments, particularly within the available domain-decomposition approach. Radiation calculations are a relatively expensive part of the atmospheric simulations taking approximately up to over 50 % of the total runtime. This current level of cost is achieved by calculating the radiative transfer only once in every two simulation hours. In response, we propose to extend the available concurrency within the model further by running the radiation component in parallel with other atmospheric processes to improve scalability and performance. This paper introduces the concurrent radiation scheme in ECHAM6 and presents a thorough analysis of its impact on the performance of the model. It also evaluates the scientific results from such simulations. Our experiments show that ECHAM6 can achieve a speedup over 1.9x using the concurrent radiation scheme. This empirical study serves as a successful example that can stimulate research on other concurrent components in atmospheric modeing whenever scalability becomes challenging.

Mohammad Reza Heidari et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2021-117', Anonymous Referee #1, 16 Jul 2021
    • CC1: 'Reply on RC1', Mohammad Reza Heidari, 27 Jul 2021
      • RC2: 'Reply on CC1', Anonymous Referee #1, 03 Aug 2021
  • RC3: 'Comment on gmd-2021-117', Robin Hogan, 27 Aug 2021

Mohammad Reza Heidari et al.

Mohammad Reza Heidari et al.


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Short summary
To improve our understanding of the climate system dynamics and its variability, the numerical atmospheric model ECHAM6 is used to simulate a complete glacial cycle over the past 120,000 years. However, performing such simulations takes very long even on the state-of-the-art supercomputers. To accelerate the model simulation, we propose to calculate radiative transfer processes in parallel with adiabatic processes in the atmosphere, which reduces the simulation time by nearly a half.