Constraining Aging Processes of Black Carbon in the Community Atmosphere Model Using Environmental Chamber Measurements

Journal Article · Tue Oct 23 00:00:00 UTC 2018 · Journal of Advances in Modeling Earth Systems

DOI: https://doi.org/10.1029/2018MS001387 · OSTI ID:1478671

Wang, Yuan  ^[1]; Ma, Po‐Lun  ^[2]; Peng, Jianfei ^[3]; Zhang, Renyi ^[3]; Jiang, Jonathan H.  ^[4]; Easter, Richard C.  ^[2]; Yung, Yuk L. ^[1]

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1. Division of Geological and Planetary Sciences California Institute of Technology Pasadena CA USA, Jet Propulsion Laboratory California Institute of Technology Pasadena CA USA
2. Atmospheric Sciences and Global Change Division Pacific Northwest National Laboratory Richland WA USA
3. Department of Atmospheric Sciences Texas A&,M University College Station TX USA
4. Jet Propulsion Laboratory California Institute of Technology Pasadena CA USA

Abstract The direct radiative forcing of black carbon aerosol (BC) on the Earth system remains unsettled, largely due to the uncertainty with physical properties of BC throughout their lifecycle. Here we show that ambient chamber measurements of BC properties provide a novel constraint on the crude BC aging representation in climate models. Observational evidence for significant absorption enhancement of BC can be reproduced when the aging processes in the four‐mode version of the Modal Aerosol Module (MAM4) aerosol scheme in the Community Atmosphere Model version 5 are calibrated by the recent in situ chamber measurements. An observation‐based scaling method is developed in the aging timescale calculation to alleviate the influence of biases in the simulated model chemical composition. Model sensitivity simulations suggest that the different monolayer settings in the BC aging parameterization of MAM4 can cause as large as 26% and 24% differences in BC burden and radiative forcing, respectively. We also find that an increase in coating materials (e.g., sulfate and secondary organic aerosols) reduces BC lifetime by increasing the hygroscopicity of the mixture but enhances its absorption, resulting in a net increase in BC direct radiative forcing. Our results suggest that accurate simulations of BC aging processes as well as other aerosol species are equally important in reducing the uncertainty of BC forcing estimation.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1478671
• Report Number(s): PNNL-SA--139085
• Journal Information: Journal of Advances in Modeling Earth Systems, Journal Name: Journal of Advances in Modeling Earth Systems Journal Issue: 10 Vol. 10; ISSN 1942-2466
• Publisher: American Geophysical Union (AGU)Copyright Statement
• Country of Publication: United States
• Language: English