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Distinct responses of Asian summer monsoon to black carbon aerosols and greenhouse gases

Publication ,  Journal Article
Xie, X; Myhre, G; Liu, X; Li, X; Shi, Z; Wang, H; Kirkevåg, A; Lamarque, JF; Shindell, D; Takemura, T; Liu, Y
Published in: Atmospheric Chemistry and Physics
October 21, 2020

Black carbon (BC) aerosols emitted from natural and anthropogenic sources induce positive radiative forcing and global warming, which in turn significantly affect the Asian summer monsoon (ASM). However, many aspects of the BC effect on the ASM remain elusive and largely inconsistent among previous studies, which is strongly dependent on different low-level thermal feedbacks over the Asian continent and the surrounding ocean. This study examines the response of the ASM to BC forcing in comparison with the effect of doubled greenhouse gases (GHGs) by analyzing the Precipitation Driver Response Model Intercomparison Project (PDRMIP) simulations under an extremely high BC level (10 times modern global BC emissions or concentrations, labeled BC×10) from nine global climate models (GCMs). The results show that although BC and GHGs both enhance the ASM precipitation minus evaporation (P -E; a 13.6% increase for BC forcing and 12.1% for GHGs from the nine-model ensemble, respectively), there exists a much larger uncertainty in changes in ASM P -E induced by BC than by GHGs. The summer P -E is increased by 7.7% to 15.3% due to these two forcings over three subregions, including East Asian, South Asian and western North Pacific monsoon regions. Further analysis of moisture budget reveals distinct mechanisms controlling the increases in ASM P -E induced by BC and GHGs. The change in ASM P -E by BC is dominated by the dynamic effect due to the enhanced large-scale monsoon circulation, whereas the GHGinduced change is dominated by the thermodynamic effect through increasing atmospheric water vapor. Radiative forcing of BC significantly increases the upper-level atmospheric temperature over the Asian region to enhance the upper-level meridional land-sea thermal gradient (MLOTG), resulting in a northward shift of the upper-level subtropical westerly jet and an enhancement of the low-level monsoon circulation, whereas radiative forcing of GHGs significantly increases the tropical upper-level temperature, which reduces the upperlevel MLOTG and suppresses the low-level monsoonal circulation. Hence, our results indicate a different mechanism of BC climate effects under the extremely high BC level: That BC forcing significantly enhances the upper-level atmospheric temperature over the Asian region, determining ASM changes, instead of low-level thermal feedbacks as indicated by previous studies.

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Published In

Atmospheric Chemistry and Physics

DOI

EISSN

1680-7324

ISSN

1680-7316

Publication Date

October 21, 2020

Volume

20

Issue

20

Start / End Page

11823 / 11839

Related Subject Headings

  • Meteorology & Atmospheric Sciences
  • 3702 Climate change science
  • 3701 Atmospheric sciences
  • 0401 Atmospheric Sciences
  • 0201 Astronomical and Space Sciences
 

Citation

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Xie, X., Myhre, G., Liu, X., Li, X., Shi, Z., Wang, H., … Liu, Y. (2020). Distinct responses of Asian summer monsoon to black carbon aerosols and greenhouse gases. Atmospheric Chemistry and Physics, 20(20), 11823–11839. https://doi.org/10.5194/acp-20-11823-2020
Xie, X., G. Myhre, X. Liu, X. Li, Z. Shi, H. Wang, A. Kirkevåg, et al. “Distinct responses of Asian summer monsoon to black carbon aerosols and greenhouse gases.” Atmospheric Chemistry and Physics 20, no. 20 (October 21, 2020): 11823–39. https://doi.org/10.5194/acp-20-11823-2020.
Xie X, Myhre G, Liu X, Li X, Shi Z, Wang H, et al. Distinct responses of Asian summer monsoon to black carbon aerosols and greenhouse gases. Atmospheric Chemistry and Physics. 2020 Oct 21;20(20):11823–39.
Xie, X., et al. “Distinct responses of Asian summer monsoon to black carbon aerosols and greenhouse gases.” Atmospheric Chemistry and Physics, vol. 20, no. 20, Oct. 2020, pp. 11823–39. Scopus, doi:10.5194/acp-20-11823-2020.
Xie X, Myhre G, Liu X, Li X, Shi Z, Wang H, Kirkevåg A, Lamarque JF, Shindell D, Takemura T, Liu Y. Distinct responses of Asian summer monsoon to black carbon aerosols and greenhouse gases. Atmospheric Chemistry and Physics. 2020 Oct 21;20(20):11823–11839.

Published In

Atmospheric Chemistry and Physics

DOI

EISSN

1680-7324

ISSN

1680-7316

Publication Date

October 21, 2020

Volume

20

Issue

20

Start / End Page

11823 / 11839

Related Subject Headings

  • Meteorology & Atmospheric Sciences
  • 3702 Climate change science
  • 3701 Atmospheric sciences
  • 0401 Atmospheric Sciences
  • 0201 Astronomical and Space Sciences