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Communication Dans Un Congrès Année : 2023

Identification of Mixed-Phase Clouds Using Combined CALIPSO Lidar and Imaging Infrared Radiometer Observations

Résumé

Using the so-called Hu diagram relating layer-integrated depolarization ratio (δv) and layer-integrated attenuated backscatter at 532 nm (γ′532), the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar can effectively discriminate between liquid water clouds, clouds composed of randomly oriented ice (ROI) crystals, and ice clouds that contain some fraction of horizontally oriented ice (HOI) crystals. A recently proposed Hu diagram update splits the original water region into a more compact pure liquid regime and two mixed-phase regions. We propose an extended Hu diagram that additionally identifies mixed-phase clouds by incorporating perfectly colocated microphysical index (βeff) and effective diameter (De) retrievals in the thermal infrared window obtained from the CALIPSO imaging infrared radiometer (IIR). First, using the βeff index, we identify regions of the Hu diagram which are seemingly associated with mixed-phase clouds. Second, we characterize opaque water clouds in the updated Hu diagram. Water clouds with top temperatures lower than 238 K, when ice is expected in the upper portion of the cloud, fall distinctly into a proposed mixed-phase region. IIR De varies as expected with lidar ratio in the tighter liquid water region and is larger due to the presence of ice in the mixed-phase region. Finally, we show that the HOI class clusters into two main families of δv-γ′532 relationships, suggesting mixed-phase clouds with smaller De and pure ice clouds with larger De, which is confirmed by Monte Carlo simulations published in the literature.
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Dates et versions

insu-04374328 , version 1 (05-01-2024)

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Anne Garnier, Jacques Pelon, David Winker, Melody Avery, Mark A. Vaughan, et al.. Identification of Mixed-Phase Clouds Using Combined CALIPSO Lidar and Imaging Infrared Radiometer Observations. ILRC 30: Proceedings of the 30th International Laser Radar Conference, Jun 2022, Big Sky, Montana, United States. pp.817-823, ⟨10.1007/978-3-031-37818-8_105⟩. ⟨insu-04374328⟩
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