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Title: How does increasing horizontal resolution in a global climate model improve the simulation of aerosol-cloud interactions?

We report the Community Atmosphere Model Version 5 is run at horizontal grid spacing of 2, 1, 0.5, and 0.25°, with the meteorology nudged toward the Year Of Tropical Convection analysis, and cloud simulators and the collocated A-Train satellite observations are used to explore the resolution dependence of aerosol-cloud interactions. The higher-resolution model produces results that agree better with observations, showing an increase of susceptibility of cloud droplet size, indicating a stronger first aerosol indirect forcing (AIF), and a decrease of susceptibility of precipitation probability, suggesting a weaker second AIF. The resolution sensitivities of AIF are attributed to those of droplet nucleation and precipitation parameterizations. Finally, the annual average AIF in the Northern Hemisphere midlatitudes (where most anthropogenic emissions occur) in the 0.25° model is reduced by about 1 W m -2 (-30%) compared to the 2° model, leading to a 0.26 W m -2 reduction (-15%) in the global annual average AIF.
Authors:
 [1] ;  [1] ; ORCiD logo [2] ;  [1] ; ORCiD logo [1] ;  [1] ; ORCiD logo [1] ;  [3] ;  [4] ;  [4]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Atmospheric Sciences and Global Change Division
  2. Nanjing University (China). Institute for Climate and Global Change Research and School of Atmospheric Sciences; Jiangsu Collaborative Innovation Center of Climate Change, Nanjing (China)
  3. University of Wyoming, Laramie, WY (United States). Department of Atmospheric Science
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Program for Climate Model Diagnosis and Intercomparison
Publication Date:
Report Number(s):
LLNL-JRNL-741123
Journal ID: ISSN 0094-8276
Grant/Contract Number:
AC52-07NA27344; AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 42; Journal Issue: 12; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1409986