Global analysis of cloud phase and ice crystal orientation from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data using attenuated backscattering and depolarization ratio

R. Yoshida, Hajime Okamoto, Y. Hagihara, H. Ishimoto

研究成果: ジャーナルへの寄稿記事

70 引用 (Scopus)

抄録

A method for discriminating cloud particle types was developed using lidar backscattering copolarization and cross-polarization channel measurements from Cloud-Aerosol Lidar With Orthogonal Polarization (CALIOP) on board Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). In spaceborne lidar measurements, significant multiple scattering effects discriminate between cloud water and ice difficult using the depolarization ratio (δ). We theoretically estimated the relationship between δ and cloud extinction on the basis of the backward Monte Carlo method. Cloud particle type was determined by the combined use of δ and the ratio of attenuated backscattering coefficients for two vertically consecutive layers. Ice particles were further classified into two categories: randomly oriented ice crystals (3-D ice) and horizontally oriented plates (2-D plate). The method was applied to CALIOP data for September-November 2006. We found that 3-D ice generally occurred colder than -20°C, whereas 2-D plate occurred between -10°C and -20°C, with high-occurrence frequency in high-latitude regions. We compared the results to those obtained using the vertical feature mask (VFM). The VFM tended to show a homogeneous cloud type through the entire cloud layer in vertical directions and misclassified 2-D plate as water. The ratio of water particles relative to ice particles decreased with decreasing temperature. By the proposed method, water cloud occurrence in subtropical and high-latitude regions was greater (up to 20%) than in the other regions below -10°C; however, the VFM results did not show such dependence on latitude. Comparison of ice and water cloud between our results and Moderate Resolution Imaging Spectroradiometer (MODIS) products showed better agreement for water cloud than for ice cloud.

元の言語英語
記事番号D00H32
ジャーナルJournal of Geophysical Research Atmospheres
115
発行部数16
DOI
出版物ステータス出版済み - 1 1 2010

Fingerprint

CALIPSO
lidar
satellite observation
ice crystal
Depolarization
Ice
Optical radar
Backscattering
aerosols
Aerosols
optical radar
Crystal orientation
depolarization
crystals
backscattering
ice
Satellites
Infrared radiation
cloud water
Water

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

これを引用

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title = "Global analysis of cloud phase and ice crystal orientation from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data using attenuated backscattering and depolarization ratio",
abstract = "A method for discriminating cloud particle types was developed using lidar backscattering copolarization and cross-polarization channel measurements from Cloud-Aerosol Lidar With Orthogonal Polarization (CALIOP) on board Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). In spaceborne lidar measurements, significant multiple scattering effects discriminate between cloud water and ice difficult using the depolarization ratio (δ). We theoretically estimated the relationship between δ and cloud extinction on the basis of the backward Monte Carlo method. Cloud particle type was determined by the combined use of δ and the ratio of attenuated backscattering coefficients for two vertically consecutive layers. Ice particles were further classified into two categories: randomly oriented ice crystals (3-D ice) and horizontally oriented plates (2-D plate). The method was applied to CALIOP data for September-November 2006. We found that 3-D ice generally occurred colder than -20°C, whereas 2-D plate occurred between -10°C and -20°C, with high-occurrence frequency in high-latitude regions. We compared the results to those obtained using the vertical feature mask (VFM). The VFM tended to show a homogeneous cloud type through the entire cloud layer in vertical directions and misclassified 2-D plate as water. The ratio of water particles relative to ice particles decreased with decreasing temperature. By the proposed method, water cloud occurrence in subtropical and high-latitude regions was greater (up to 20{\%}) than in the other regions below -10°C; however, the VFM results did not show such dependence on latitude. Comparison of ice and water cloud between our results and Moderate Resolution Imaging Spectroradiometer (MODIS) products showed better agreement for water cloud than for ice cloud.",
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AU - Ishimoto, H.

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