Title: Biomass smoke from southern Africa can significantly enhance the brightness of stratocumulus over the southeastern Atlantic Ocean

Abstract

Marine stratocumulus clouds cover nearly one-quarter of the ocean surface and thus play an extremely important role in determining the global radiative balance. The semipermanent marine stratocumulus deck over the southeastern Atlantic Ocean is of particular interest, due to its interactions with seasonal biomass burning aerosols that are emitted in southern Africa. Understanding the impacts of biomass burning aerosols on stratocumulus clouds and the implications for regional and global radiative balance is still very limited. Previous studies have focused on assessing the magnitude of the warming caused by solar scattering and absorption by biomass burning aerosols over stratocumulus (the direct radiative effect) or cloud adjustments to the direct radiative effect (the semidirect effect). Here, using a nested modeling approach in conjunction with observations from multiple satellites, we demonstrate that cloud condensation nuclei activated from biomass burning aerosols entrained into the stratocumulus (the microphysical effect) can play a dominant role in determining the total radiative forcing at the top of the atmosphere, compared with their direct and semidirect radiative effects. Biomass burning aerosols over the region and period with heavy loadings can cause a substantial cooling (daily mean –8.05 W m^–2), primarily as a result of clouds brightening by reducing themore » cloud droplet size (the Twomey effect) and secondarily through modulating the diurnal cycle of cloud liquid water path and coverage (the cloud lifetime effect). Our findings illustrate the significance of realistically representing the interactions of stratocumulus with biomass burning aerosols in global climate models in this region.« less

Authors:

Lu, Zheng ^[1]; Liu, Xiaohong ^[2]; Zhang, Zhibo ^[3]; Zhao, Chun ^[4]; Meyer, Kerry  ^[5];

• Search DOE PAGES for author "Meyer, Kerry"
• Search DOE PAGES for ORCID "0000-0001-5361-9200"

Rajapakshe, Chamara  ^[6];

• Search DOE PAGES for author "Rajapakshe, Chamara"
• Search DOE PAGES for ORCID "0000-0002-7264-9867"

Wu, Chenglai  ^[2];

• Search DOE PAGES for author "Wu, Chenglai"
• Search DOE PAGES for ORCID "0000-0002-8397-2424"

Yang, Zhifeng ^[3]; Penner, Joyce E. ^[7]

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+ Show Author Affiliations

1. Department of Atmospheric Science, University of Wyoming, Laramie, WY 82071,
2. Department of Atmospheric Science, University of Wyoming, Laramie, WY 82071,, International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China,
3. Physics Department, University of Maryland Baltimore County, Baltimore, MD 21250,, Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD 21250,
4. School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China,
5. Climate and Radiation Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771,
6. Physics Department, University of Maryland Baltimore County, Baltimore, MD 21250,
7. Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109

Publication Date:

Mon Mar 05 00:00:00 EST 2018

Research Org.:

Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States)

Sponsoring Org.:

USDOE Office of Science (SC); National Science Foundation (NSF)

OSTI Identifier:

1423733

Alternate Identifier(s):

OSTI ID: 1540268

Grant/Contract Number:  

NSF-DOE-USDA Joint Earth System Modeling (EaSM) Program; SC0014641

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 115 Journal Issue: 12; Journal ID: ISSN 0027-8424

Publisher:

Proceedings of the National Academy of Sciences

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; stratocumulus clouds; biomass burning aerosols; aerosol–cloud interaction