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

Journal Article · Thu Jul 14 00:00:00 EDT 2022 · Atmospheric Chemistry and Physics

DOI:https://doi.org/10.5194/acp-2021-1087· OSTI ID:1877062

Zhang, Kai  ^[1]; Zhang, Wentao ^[2]; Wan, Hui  ^[1]; Rasch, Philip J. ^[1]; Ghan, Steven J. ^[1]; Easter, Richard C.  ^[1]; Shi, Xiangjun  ^[3]; Wang, Yong ^[4]; Wang, Hailong  ^[1]; Ma, Po-Lun  ^[1]; Zhang, Shixuan  ^[1]; Sun, Jian ^[1]; Burrows, Susannah  ^[1]; Shrivastava, Manish  ^[1]; Singh, Balwinder ^[1]; Qian, Yun ^[1]; Liu, Xiaohong ^[5]; Golaz, Jean-Christophe  ^[6]; Tang, Qi  ^[6]; Zheng, Xue  ^[6] ; Xie, Shaocheng ^[6]; Lin, Wuyin  ^[7]; Feng, Yan  ^[8]; Wang, Minghuai  ^[9]; Yoon, Jin-Ho  ^[10]; Leung, Ruby L.  ^[1]

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1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2. Nanjing University of Information Science and Technology (China); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
3. Nanjing University of Information Science and Technology (China)
4. Tsinghua University, Beijing (China)
5. Texas A & M University, College Station, TX (United States)
6. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
7. Brookhaven National Lab. (BNL), Upton, NY (United States)
8. Argonne National Lab. (ANL), Lemont, IL (United States)
9. Nanjing University (China)
10. Gwangju Institute of Science and Technology (Korea, Republic of)

The effective radiative forcing of anthropogenic aerosols (ERF_aer) is an important measure of the anthropogenic aerosol effects simulated by a global climate model. Here we analyze ERF_aer simulated by the E3SMv1 atmosphere model using both century-long free-running atmosphere-land simulations and short nudged simulations. We relate the simulated ERF_aer 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 ERF_aer 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 ERF_aer 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 ERF_aer 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 ERF_aer, it would be more effective to reduce the anthropogenic aerosol effect through liquid or mixed-phase clouds.

• Research Organization: Brookhaven National Lab. (BNL), Upton, NY (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: SC0012704; AC06-76RLO1830; AC02-06CH11357; AC52-07NA27344; NRF-2020M1A5A1110578; NRF-2021R1A2C1011827; AC02-05CH11231
• OSTI ID: 1877062
• Report Number(s): BNL-223132-2022-JAAM
• Journal Information: Atmospheric Chemistry and Physics, Vol. 22; ISSN 1680-7316
• Publisher: Copernicus Publications, EGU
• Country of Publication: United States
• Language: English

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54 ENVIRONMENTAL SCIENCES