the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
An Extensible Perturbed Parameter Ensemble (PPE) for the Community Atmosphere Model Version 6
Abstract. This paper documents the methodology and preliminary results from a Perturbed Parameter Ensemble (PPE) technique, where multiple parameters are varied simultaneously and the parameter values are determined with Latin hypercube sampling. This is done with the Community Atmosphere Model version 6 (CAM6), the atmospheric component of the Community Earth System Model version 2 (CESM2). We apply the PPE method to CESM2-CAM6 to understand climate sensitivity to atmospheric physics parameters. The initial simulations vary 45 parameters in the microphysics, convection, turbulence and aerosol schemes with 263 ensemble members. These atmospheric parameters are typically the most uncertain in many climate models. Control simulations are analyzed and targeted simulations to understand climate forcing due to aerosols and fast climate feedbacks. The use of various emulators is explored in the multi- dimensional space mapping input parameters to output metrics. Parameter impacts on various model outputs, such as radiation, cloud and aerosol properties are evaluated. Machine learning is also used to probe optimal parameter values against observations. Our findings show that using PPE is a valuable tool for climate uncertainty analysis. Furthermore, by varying many parameters simultaneously, we find that many different combinations of parameter values can produce results consistent with observations, and thus careful analysis of tuning is important. The CESM2-CAM6 PPE is publicly available, and extensible to other configurations to address questions of other model processes in the atmosphere and other model components (e.g. coupling to the land surface).
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Status: open (until 01 Jun 2024)
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RC1: 'Comment on egusphere-2023-2165', Anonymous Referee #1, 12 Feb 2024
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The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2023-2165/egusphere-2023-2165-RC1-supplement.pdf
Data sets
CESM2.2-CAM6 Perturbed Parameter Ensemble (PPE) Trude Eidhammer, Andrew Gettelman, and Katherine Thayer-Calder https://doi.org/10.26024/bzne-yf09
CERES_EBAF_Ed4.1_2001-2020 subset Trude Eidhammer and Andrew Gettelman https://zenodo.org/records/10426438
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