the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Understanding Changes in Cloud Simulations from E3SM Version 1 to Version 2
Shaocheng Xie
Wuyin Lin
Jean-Christophe Golaz
Xue Zheng
Po-Lun Ma
Yun Qian
Christopher R. Terai
Meng Zhang
Abstract. This study documents clouds simulated by the Energy Exascale Earth System Model (E3SM) version 2 (E3SMv2) and attempts to understand what causes the model behavior change in clouds relative to E3SMv1. This is done by analyzing the last 30-year (1985–2014) data from the 165-year historical simulations using E3SMv1 and v2 and four sensitivity tests to isolate the impact of changes in model parameter choices in its turbulence, shallow convection, and cloud macrophysics parameterization (CLUBB), microphysical parameterization (MG2), and deep convection scheme (ZM), as well as model physics changes in convective triggering. It is shown that E3SMv2 significantly improves the simulation of subtropical coastal stratocumulus clouds (Sc) and clouds with optical depth larger than 3.6 over the stratocumulus to cumulus transition regimes, where Shortwave Cloud Radiative Effect (SWCRE) is also improved, and the Southern Ocean (SO) while seeing an overall slight degradation in low clouds over other tropical and subtropical oceans. The better performance in E3SMv1 over those regions is partially due to error compensation between its simulated optically thin and intermediate low clouds for which E3SMv2 actually improves simulation of optically intermediate low clouds. Sensitivity tests indicate that the changes in low clouds are primarily due to the tuning made in CLUBB. The impact of the ZM tuning is mainly on optically intermediate and thick high clouds, contributing to improved SWCRE and Longwave Cloud Radiative Effect (LWCRE). The impact of the MG2 tuning and the new convective trigger is primarily on the high latitudes and the Southern Ocean (SO). They have a relatively smaller impact on clouds than do the CLUBB and ZM tunings. This study offers additional insights about clouds simulated in E3SMv2 by utilizing multiple data sets and the COSP diagnostic tool as well as through sensitivity tests. The improved understanding will benefit the future E3SM developments.
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Yuying Zhang et al.
Status: open (until 07 Oct 2023)
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RC1: 'Comment on egusphere-2023-1263', Anonymous Referee #1, 21 Aug 2023
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This study attempts to understand cloud changes induced by the E3SM version change from version 1 (E3SMv1) to version 2 (E3SMv2) with comparisons between E3SM COSP simulator results and corresponding satellite data. Also, the authors try to decompose the cause of cloud change from changes in each physics scheme (MG2, CLUBB, and ZM). This paper seems to achieve the authors' goal of showing the cloud changes of the newly released version of the model and which process influences those changes. I think this paper is valuable to be published after some revisions.
Main Comment
- For the sensitivity tests, it will be more helpful for the reader’s understanding if the authors can explain more about the parameter tuning and dCAPE_ULL trigger (object and results, briefly) even though the authors already refer to Ma et al. (2022), Golaz et al. (2022), and Qin et al. (2023).
- I think some modifications can improve Section 4. Section 4 comprises many figures and explanations for the figures, but the objective for Section 4 does not seem clear to me. I think there might be two different ways:
- Simplify Section 4 and concentrate more on the connection between Figures 7~11 and 12~17.
- Describe details about how the newly adapted processes in E3SMv2 derive the differences in figures 12~17.
- Some comments for specific sentences
- Line 146~148: If a reference can be added, it will be helpful.
- Line 196~197: If authors explain more about the “additional information”, it will be helpful.
- Table 1: How about adding some information about temporal and spatial resolution, which might be different from each other?
Technical Comment
- Both τ and Tau are used in the manuscript. It seems better to select one of them to avoid confusion.
- Both N.H. and N. Hemisphere are used. It seems better to select one of them to avoid confusion.
- Line 200: reginal->regional
- Line 540: cloud fraction->CRE
Citation: https://doi.org/10.5194/egusphere-2023-1263-RC1 -
AC1: 'Reply on RC1', Yuying Zhang, 24 Sep 2023
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The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1263/egusphere-2023-1263-AC1-supplement.pdf
Yuying Zhang et al.
Yuying Zhang et al.
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