Impact of ice cloud microphysics on satellite cloud retrievals and broadband flux radiative transfer model calculations

Norman G. Loeb, Ping Yang, Fred G. Rose, Gang Hong, Sunny Sun-Mack, Patrick Minnis, Seiji Kato, Seung Hee Ham, William L. Smith, Souichiro Hioki, Guanglin Tang

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Ice cloud particles exhibit a range of shapes and sizes affecting a cloud's single-scattering properties. Because they cannot be inferred from passive visible/infrared imager measurements, assumptions about the bulk single-scattering properties of ice clouds are fundamental to satellite cloud retrievals and broadband radiative flux calculations. To examine the sensitivity to ice particle model assumptions, three sets of models are used in satellite imager retrievals of ice cloud fraction, thermodynamic phase, optical depth, effective height, and particle size, and in top-of-atmosphere (TOA) and surface broadband radiative flux calculations. The three ice particle models include smooth hexagonal ice columns (SMOOTH), roughened hexagonal ice columns, and a two-habit model (THM) comprising an ensemble of hexagonal columns and 20-element aggregates. While the choice of ice particle model has a negligible impact on daytime cloud fraction and thermodynamic phase, the global mean ice cloud optical depth retrieved from THM is smaller than from SMOOTH by 2.3 (28%), and the regional root-mean-square difference (RMSD) is 2.8 (32%). Effective radii derived from THM are 3.9 μm (16%) smaller than SMOOTH values and the RMSD is 5.2 μm (21%). In contrast, the regional RMSD in TOA and surface flux between THM and SMOOTH is only 1% in the shortwave and 0.3% in the longwave when a consistent ice particle model is assumed in the cloud property retrievals and forward radiative transfer model calculations. Consequently, radiative fluxes derived using a consistent ice particle model assumption throughout provide a more robust reference for climate model evaluation compared to ice cloud property retrievals.

Original languageEnglish (US)
Pages (from-to)1851-1864
Number of pages14
JournalJournal of Climate
Volume31
Issue number5
DOIs
StatePublished - Mar 1 2018
Externally publishedYes

Keywords

  • Cirrus clouds
  • Cloud microphysics
  • Cloud retrieval
  • Model evaluation/performance
  • Radiation budgets

ASJC Scopus subject areas

  • Atmospheric Science

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