Simulated responses of terrestrial aridity to black carbon and sulfate aerosols

Journal Article · Wed Jan 27 04:00:00 UTC 2016 · Journal of Geophysical Research: Atmospheres

DOI: https://doi.org/10.1002/2015JD024100 · OSTI ID:1438461

Lin, L. ^[1]; Gettelman, A. ^[2]; Xu, Y. ^[2]; Fu, Q. ^[3]

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1. Lanzhou Univ. (China). College of Atmospheric Sciences; National Center for Atmospheric Research
2. National Center for Atmospheric Research, Boulder, CO (United States)
3. Lanzhou Univ. (China). College of Atmospheric Sciences; Univ. of Washington, Seattle, WA (United States). Dept. of Atmospheric Sciences

Aridity index (AI), defined as the ratio of precipitation to potential evapotranspiration (PET), is a measure of the dryness of terrestrial climate. Global climate models generally project future decreases of AI (drying) associated with global warming scenarios driven by increasing greenhouse gas and declining aerosols. Given their different effects in the climate system, scattering and absorbing aerosols may affect AI differently. In this work, we explore the terrestrial aridity responses to anthropogenic black carbon (BC) and sulfate (SO₄) aerosols with Community Earth System Model simulations. Positive BC radiative forcing decreases precipitation averaged over global land at a rate of 0.9%/°C of global mean surface temperature increase (moderate drying), while BC radiative forcing increases PET by 1.0%/°C (also drying). BC leads to a global decrease of 1.9%/°C in AI (drying). SO₄ forcing is negative and causes precipitation a decrease at a rate of 6.7%/°C cooling (strong drying). PET also decreases in response to SO₄ aerosol cooling by 6.3%/°C cooling (contributing to moistening). Thus, SO₄ cooling leads to a small decrease in AI (drying) by 0.4%/°C cooling. Despite the opposite effects on global mean temperature, BC and SO₄ both contribute to the twentieth century drying (AI decrease). Sensitivity test indicates that surface temperature and surface available energy changes dominate BC- and SO₄-induced PET changes.

• Research Organization: National Center for Atmospheric Research, Boulder, CO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Natural Science Foundation of China (NSFC); National Basic Research Program of China (973 Program); Fundamental Research Funds for the Central Universities (China); National Science Foundation (NSF)
• Grant/Contract Number: FC02-97ER62402
• OSTI ID: 1438461
• Journal Information: Journal of Geophysical Research: Atmospheres, Journal Name: Journal of Geophysical Research: Atmospheres Journal Issue: 2 Vol. 121; ISSN 2169-897X
• Publisher: American Geophysical UnionCopyright Statement
• Country of Publication: United States
• Language: English