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Korolev A, McFarquhar G, Field PR, Franklin C, Lawson P, Wang Z, Williams E, Abel SJ, Axisa D, Borrmann S, Crosier J, Fugal J, Krämer M, Lohmann U, Schlenczek O, Schnaiter M, Wendisch M. Mixed-Phase Clouds: Progress and Challenges. ACTA ACUST UNITED AC 2017. [DOI: 10.1175/amsmonographs-d-17-0001.1] [Citation(s) in RCA: 120] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- A. Korolev
- Environment and Climate Change Canada, Toronto, Ontario, Canada
| | - G. McFarquhar
- University of Illinois at Urbana–Champaign, Urbana, Illinois
| | - P. R. Field
- Met Office, Exeter, United Kingdom
- University of Leeds, Leeds, United Kingdom
| | - C. Franklin
- Bureau of Meteorology, Melbourne, Victoria, Australia
| | - P. Lawson
- Stratton Park Engineering Corporation, Boulder, Colorado
| | - Z. Wang
- University of Wyoming, Laramie, Wyoming
| | - E. Williams
- Massachusetts Institute of Technology, Cambridge, Massachusetts
| | | | - D. Axisa
- National Center for Atmospheric Research, Boulder, Colorado
| | - S. Borrmann
- Max Planck Institute for Chemistry, Mainz, Germany
| | - J. Crosier
- School of Earth and Environment, University of Manchester, Manchester, United Kingdom
- National Centre for Atmospheric Science, University of Manchester, Manchester, United Kingdom
| | - J. Fugal
- Institute for Atmospheric Physics, University of Mainz, Mainz, Germany
| | - M. Krämer
- Forschungszentrum Jülich, Jülich, Germany
| | - U. Lohmann
- ETH Zurich, Institute for Atmospheric and Climate Science, Zurich, Switzerland
| | - O. Schlenczek
- Institute for Atmospheric Physics, University of Mainz, Mainz, Germany
| | - M. Schnaiter
- Karlsruhe Institute of Technology, Karlsruhe, Germany
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van Diedenhoven B, Ackerman AS, Fridlind AM, Cairns B. On averaging aspect ratios and distortion parameters over ice crystal population ensembles for estimating effective scattering asymmetry parameters. JOURNAL OF THE ATMOSPHERIC SCIENCES 2016; 73:775-787. [PMID: 28983127 PMCID: PMC5625167 DOI: 10.1175/jas-d-15-0150.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The use of ensemble-average values of aspect ratio and distortion parameter of hexagonal ice prisms for the estimation of ensemble-average scattering asymmetry parameters is evaluated. Using crystal aspect ratios greater than unity generally leads to ensemble-average values of aspect ratio that are inconsistent with the ensemble-average asymmetry parameters. When a definition of aspect ratio is used that limits the aspect ratio to below unity (α≤1) for both hexagonal plates and columns, the effective asymmetry parameters calculated using ensemble-average aspect ratios are generally consistent with ensemble-average asymmetry parameters, especially if aspect ratios are geometrically averaged. Ensemble-average distortion parameters generally also yield effective asymmetry parameters that are largely consistent with ensemble-average asymmetry parameters. In the case of mixtures of plates and columns, it is recommended to geometrically average the α≤1 aspect ratios and to subsequently calculate the effective asymmetry parameter using a column or plate geometry when the contribution by columns to a given mixture's total projected area is greater or lower than 50%, respectively. In addition, we show that ensemble-average aspect ratios, distortion parameters and asymmetry parameters can generally be retrieved accurately from simulated multi-directional polarization measurements based on mixtures of varying columns and plates. However, such retrievals tend to be somewhat biased toward yielding column-like aspect ratios. Furthermore, generally large retrieval errors can occur for mixtures with approximately equal contributions of columns and plates and for ensembles with strong contributions of thin plates.
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Affiliation(s)
| | | | | | - Brian Cairns
- NASA Goddard Institute for Space Research, New York, NY
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