Preprints
https://doi.org/10.5194/acp-2021-1087
https://doi.org/10.5194/acp-2021-1087
 
07 Jan 2022
07 Jan 2022
Status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Effective radiative forcing of anthropogenic aerosols in E3SMv1: historical changes, causality, decomposition, and parameterization sensitivities

Kai Zhang1, Wentao Zhang2,1, Hui Wan1, Philip J. Rasch1, Steven J. Ghan1, Richard C. Easter1, Xiangjun Shi2, Yong Wang3, Hailong Wang1, Po-Lun Ma1, Shixuan Zhang1, Jian Sun1,a, Susannah Burrows1, Manish Shrivastava1, Balwinder Singh1, Yun Qian1, Xiaohong Liu4, Jean-Christophe Golaz5, Qi Tang5, Xue Zheng5, Shaocheng Xie5, Wuyin Lin6, Yan Feng7, Minghuai Wang8, Jin-Ho Yoon9, and Ruby L. Leung1 Kai Zhang et al.
  • 1Pacific Northwest National Laboratory, Richland, WA, USA
  • 2School of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, China
  • 3Ministry of Education Key Laboratory for Earth System Modeling and Department of Earth System Science, Tsinghua University, Beijing, China
  • 4Department of Atmospheric Sciences, Texas A&M University, College Station, Texas, USA
  • 5Lawrence Livermore National Laboratory, Livermore, CA, USA
  • 6Brookhaven National Laboratory, Upton, NY, USA
  • 7Argonne National Laboratory, Lemont, IL, USA
  • 8Nanjing University, Nanjing, China
  • 9Gwangju Institute of Science and Technology, Gwangju, South Korea
  • anow at: National Center for Atmospheric Research, Boulder, Colorado, USA

Abstract. The effective radiative forcing of anthropogenic aerosols (ERFaer) is an important measure of the anthropogenic aerosol effects simulated by a global climate model. Here we analyze ERFaer simulated by the E3SMv1 atmosphere model using both century-long free-running atmosphere-land simulations and short nudged simulations. We relate the simulated ERFaer to characteristics of the aerosol composition and optical properties, and evaluate the relationships between key aerosol and cloud properties.

In terms of historical changes from the year 1870 to 2014, our results show that the global mean anthropogenic aerosol burden and optical depth increase during the simulation period as expected, but the regional averages show large differences in the temporal evolution. The largest regional differences are found in the emission-induced evolution of the burden and optical depth of the sulfate aerosol: a strong decreasing trend is seen in the Northern Hemisphere high-latitude region after around 1970, while a continued increase is simulated in the tropics. Consequently, although the global mean anthropogenic aerosol burden and optical depth increase from 1870 to 2014, the ERFaer magnitude does not increase after around year 1970. The relationships between key aerosol and cloud properties (relative changes between preindustrial and present-day conditions) also show evident changes after 1970, diverging from the linear relationships exhibited for the period from 1870 to 2014.

The ERFaer in E3SMv1 is relatively large compared to the recently published multi-model estimates; the primary reason is the large indirect aerosol effect (i.e., through aerosol-cloud interactions). Compared to other models, E3SMv1 features a stronger sensitivity of the cloud droplet effective radius to changes in the cloud droplet number concentration. Large sensitivity is also seen in the liquid cloud optical depth, which is determined by changes in both the effective radius and liquid water path. Aerosol-induced changes in liquid and ice cloud properties in E3SMv1 are found to have a strong correlation, as the evolution of anthropogenic sulfate aerosols affects both the liquid cloud formation and the homogeneous ice nucleation in cirrus clouds.

The ERFaer estimates in E3SMv1 for the shortwave and longwave components are sensitive to the parameterization changes in both liquid and ice cloud processes. When the parameterization of ice cloud processes is modified, the top-of-atmosphere forcing changes in the shortwave and longwave components largely offset each other, so the net effect is negligible. This suggests that, to reduce the magnitude of the net ERFaer, it would be more effective to reduce the anthropogenic aerosol effect through liquid or mixed-phase clouds.

Kai Zhang et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-1087', Anonymous Referee #1, 19 Jan 2022
    • AC1: 'Reply on RC1', Kai Zhang, 27 Apr 2022
  • RC2: 'Review of Zhang et al.', Anonymous Referee #2, 18 Feb 2022
    • AC2: 'Reply on RC2', Kai Zhang, 27 Apr 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-1087', Anonymous Referee #1, 19 Jan 2022
    • AC1: 'Reply on RC1', Kai Zhang, 27 Apr 2022
  • RC2: 'Review of Zhang et al.', Anonymous Referee #2, 18 Feb 2022
    • AC2: 'Reply on RC2', Kai Zhang, 27 Apr 2022

Kai Zhang et al.

Data sets

Data to reproduce the tables and figures presented in this study Kai Zhang https://doi.org/10.5281/zenodo.5792600

Model code and software

E3SMv1 (maint-1.0) source code used in this study E3SM developers https://doi.org/10.5281/zenodo.5794575

Kai Zhang et al.

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Short summary
Here we analyze effective aerosol forcing simulated by E3SMv1 using both century-long free-running and short nudged simulations. The aerosol forcing in E3SMv1 is relatively large compared to other models, mainly due to the large indirect aerosol effect. Aerosol-induced changes in liquid and ice cloud properties in E3SMv1 have a strong correlation. The aerosol forcing estimates in E3SMv1 are sensitive to the parameterization changes in both liquid and ice cloud processes.
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