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A Positive Iris Feedback: Insights from Climate Simulations with Temperature-Sensitive Cloud-Rain Conversion

Title
A Positive Iris Feedback: Insights from Climate Simulations with Temperature-Sensitive Cloud-Rain Conversion
Authors
Li, R. L.Storelvmo, T.Fedorov, A., VChoi, Y-S
Ewha Authors
최용상
SCOPUS Author ID
최용상scopus
Issue Date
2019
Journal Title
JOURNAL OF CLIMATE
ISSN
0894-8755JCR Link

1520-0442JCR Link
Citation
JOURNAL OF CLIMATE vol. 32, no. 16, pp. 5305 - 5324
Keywords
Cirrus cloudsClimate sensitivityCloud radiative effects
Publisher
AMER METEOROLOGICAL SOC
Indexed
SCIE; SCOPUS WOS
Document Type
Article
Abstract
Estimates for equilibrium climate sensitivity from current climate models continue to exhibit a large spread, from 2.1 to 4.7 K per carbon dioxide doubling. Recent studies have found that the treatment of precipitation efficiency in deep convective clouds-specifically the conversion rate from cloud condensate to rain C-p-may contribute to the large intermodel spread. It is common for convective parameterization in climate models to carry a constant C-p, although its values are model and resolution dependent. In this study, we investigate how introducing a potential iris feedback, the cloud-climate feedback introduced by parameterizing C-p to increase with surface temperature, affects future climate simulations within a slab ocean configuration of the Community Earth System Model. Progressively stronger dependencies of C-p on temperature unexpectedly increase the equilibrium climate sensitivity monotonically from 3.8 to up to 4.6 K. This positive iris feedback puzzle, in which a reduction in cirrus clouds increases surface temperature, is attributed to changes in the opacity of convectively detrained cirrus. Cirrus clouds reduced largely in ice content and marginally in horizontal coverage, and thus the positive shortwave cloud radiative feedback dominates. The sign of the iris feedback is robust across different cloud macrophysics schemes, which control horizontal cloud cover associated with detrained ice. These results suggest a potentially strong but highly uncertain connection among convective precipitation, detrained anvil cirrus, and the high cloud feedback in a climate forced by increased atmospheric carbon dioxide concentrations.
DOI
10.1175/JCLI-D-18-0845.1
Appears in Collections:
엘텍공과대학 > 기후·에너지시스템공학전공 > Journal papers
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