Preprints
https://doi.org/10.5194/egusphere-2023-2667
https://doi.org/10.5194/egusphere-2023-2667
12 Feb 2024
 | 12 Feb 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Technical note: Retrieval of the supercooled liquid fraction in mixed-phase clouds from Himawari-8 observations

Ziming Wang, Husi Letu, Huazhe Shang, and Luca Bugliaro

Abstract. The supercooled liquid fraction (SLF) in mixed-phase clouds (MPCs) is an essential variable of cloud microphysical processes and climate sensitivity. However, SLF is currently calculated in spaceborne remote sensing only as the cloud phase frequency ratio of adjacent pixels, which results in a loss of the original resolution in observations of cloud liquid or ice content within MPCs. Here, we present a novel method for retrieving the SLF in MPCs based on the differences in radiative properties of supercooled liquid droplets and ice particles at visible and shortwave‐infrared channels of the geostationary Himawari-8. Liquid and ice water paths are inferred by assuming that clouds are composed of only liquid or ice, with the real cloud water path (CWP) expressed as a combination of these two water paths (SLF and 1-SLF as coefficients), and SLF is determined by referring to the CWP from CALIPSO. The statistical relatively small cloud phase spatial inhomogeneity in Himawari-8-pixel level indicates an optimal scene for the cloud retrieval. The SLF results are comparable to global SLF distributions observed by active instruments, particularly for single-layered cloud systems. While accessing the method’s feasibility, SLF averages are estimated between 74 % and 78 % in Southern Ocean stratocumulus across seasons, contrasting with a range of 29 % to 32 % in Northeast Asia. The former exhibits a minimum SLF around midday in summer and a maximum in winter, while the latter trend differs. This novel algorithm will be valuable for research to track the evolution of MPCs and constrain the related climate impact.

Ziming Wang, Husi Letu, Huazhe Shang, and Luca Bugliaro

Status: open (until 25 Mar 2024)

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  • RC1: 'Comment on egusphere-2023-2667', Anonymous Referee #1, 27 Feb 2024 reply
  • RC2: 'Comment on egusphere-2023-2667', Anonymous Referee #2, 03 Mar 2024 reply
Ziming Wang, Husi Letu, Huazhe Shang, and Luca Bugliaro
Ziming Wang, Husi Letu, Huazhe Shang, and Luca Bugliaro

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Short summary
Supercooled liquid fraction (SLF) in mixed-phase clouds is retrieved for the first time using passive geostationary satellite observations based on differences in liquid droplet and ice particle radiative properties. The retrieved results are well comparable to global distributions observed by active instruments, and the feasibility of the retrieval method to analyze the observed trends of SLF has been validated.