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Impact of Cloud Ice Particle Size Uncertainty in a Climate Model and Implications for Future Satellite Missions

Wang, Yuan and Su, Hui and Jiang, Jonathan H. and Xu, Feng and Yung, Yuk L. (2020) Impact of Cloud Ice Particle Size Uncertainty in a Climate Model and Implications for Future Satellite Missions. Journal of Geophysical Research. Atmospheres, 125 (6). Art. No. e2019JD032119. ISSN 2169-897X. doi:10.1029/2019jd032119.

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Ice particle size is pivotal to determining ice cloud radiative effect and precipitating rate. However, there is a lack of accurate ice particle effective radius (R_(ei)) observation on the global scale to constrain its representation in climate models. In support of future mission design, here we present a modeling assessment of the sensitivity of climate simulations to R_(ei) and quantify the impact of the proposed mission concept on reducing the uncertainty in climate sensitivity. We perturb the parameters pertaining to ice fall speed parameter and R_(ei) in radiation scheme, respectively, in National Center for Atmospheric Research CESM1 model with a slab ocean configuration. The model sensitivity experiments show that a settling velocity increase due to a larger R_(ei) results in a longwave cooling dominating over a shortwave warming, a global mean surface temperature decrease, and precipitation suppression. A similar competition between longwave and shortwave cloud forcing changes also exists when perturbing R_(ei) in the radiation scheme. Linearity generally holds for the climate response for R_(ei) related parameters. When perturbing falling snow particle size (R_(es)) in a similar way, we find much less sensitivity of climate responses. Our quadrupling CO₂ experiments with different parameter settings reveal that R_(ei) and R_(es) can account for changes in climate sensitivity significantly from +12.3% to −6.2%. By reducing the uncertainty ranges of R_(ei) and R_(es) from a factor of 2 to ±25%, a future satellite mission under design is expected to improve the climate state simulations and reduce the climate sensitivity uncertainty pertaining to ice particle size by approximately 60%. Our results highlight the importance of better observational constraints on R_(ei) by satellite missions.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wang, Yuan0000-0001-6657-8401
Su, Hui0000-0003-1265-9702
Jiang, Jonathan H.0000-0002-5929-8951
Xu, Feng0000-0001-5155-9478
Yung, Yuk L.0000-0002-4263-2562
Additional Information:© 2020 American Geophysical Union. Received 26 NOV 2019; Accepted 5 MAR 2020; Accepted article online 10 MAR 2020. This work was conducted at the NASA‐sponsored Jet Propulsion Laboratory (JPL), California Institute of Technology. All the climate model simulate output used for this research can be downloaded from this website (‐2020‐JGR‐Ice/). The code of NCAR CESM model used in this study is available at this site ( We also acknowledge high‐performance computing support from Pleiades provided at NASA Ames. All requests for materials in this paper should be addressed to Yuan Wang (
Funding AgencyGrant Number
Subject Keywords:ice clouds; climate modeling; climate sensitivity; ice effective radius
Issue or Number:6
Record Number:CaltechAUTHORS:20200408-132401922
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Official Citation:Wang, Y., Su, H., Jiang, J. H., Xu, F., & Yung, Y. L. (2020). Impact of cloud ice particle size uncertainty in a climate model and implications for future satellite missions. Journal of Geophysical Research: Atmospheres, 125, e2019JD032119.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102404
Deposited By: Tony Diaz
Deposited On:08 Apr 2020 20:39
Last Modified:16 Nov 2021 18:11

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